# Algae: the reason it grows in our tanks



## Zapins (Jul 28, 2004)

*The golden question:*


BryceM said:


> I got into a discussion with an individual a while ago about algae control. We tossed a bunch of ideas back and forth. We agreed on a few points and disagreed about others. I told him that, when in doubt, that if you address the needs of the plants, algae problems "magically" go away.


After reading BryceM's statement in another thread I started thinking about why algae problems "magically" disappear, and I believe I have arrived at a reasonable explanation that gets at the root of why all types of algae occur in our tanks (excuse the long post!).

*The observation:* 
In past experience, I have seen decent plant growth in green water blooms and even in green dust algae (GDA) blooms. The plants still grew and didn't seem to have any deficiencies, but the algae was definitely all over the tank. Similarly plants still grow perfectly well with cladophora or black beard algae (BBA) growing in the tank in visible quantities. What is the connection?

*The explanation:*
I think if bloom criteria (trigger) are met, algae will bloom whether or not the plants are doing well. This makes sense with observing algae blooms in the wild. Blooms of certain species of algae appear at distinct times of the year in direct relation to nutrient concentrations, presence of predators, seasonal events (for example: an excess of one nutrient due to rains, or a lack of another due to no rains, etc...).

For example, if a particular species of algae is environmentally cued to bloom when nitrate levels are low for a few days, it will bloom. Since most plants can stockpile nutrients to last them a week at the very least, the plants still have nitrogen available to grow with, they are not deficient yet so the problem isn't that the plant is unhappy which causes the algae to bloom, it is rather the fact that the species of algae is genetically programmed to recognize a particular set of conditions in order to grow.

It is possible that the plant will quickly begin to suffer after an algae bloom gets started since they are already running off reserves and now have to devote more energy and scarce nutrients towards the task of scouring the water for trace concentrations of the lacking nutrient.

I think the statement that "algae = poor plant growth" is usually the case, but I don't think it is 100% accurate in every situation. I think this association tends to be true because people generally don't realize that there is a problem until an algae bloom has been triggered and the plants have depleted their reserves. Since it takes quite a long time for a weakened plant to fully recover and produce heavy new growth after it has been stressed it makes sense that algae, requiring far fewer nutrients to get by, would run rampant until the blooming criteria are fixed and the plants resume their normal roles.

Going along with this idea, I think that the recommended range of nutrient levels (5-20 ppm nitrate, 2 ppm phosphate, etc...) is a range in which few species of algae are programmed to bloom at. I think this may be because over eons of time algae evolution has found it more adventitious to fill a niche in the environment that requires disturbance rather than constancy. For example, if algae and plants grew all the time, provided there were enough nutrients to support growth (i.e. plentiful nutrients 5-20 ppm nitrate, etc...), then they would have to compete with each other constantly for available food which means less energy for reproduction. The plants, being capable of blocking sunlight due to their height advantage and emergent growth could simply shade out any algae that tried to grow constantly causing it to be less successful than a species that was dormant for most of the year except when particular conditions signaled a possible advantage (like a seasonal change for example). In nature it is well documented that species who initially occupy the same niche tend to evolve away from each other over time so that their requirements do not overlap and competition is minimized thereby increasing the reproductive success of both species.

When algae blooming conditions are met (i.e. unstable tank conditions favoring a particular species of algae) the algae blooms until the trigger condition is removed. Sometimes that might mean the algae has found it most effective to simply complete one life cycle and then return to dormancy (GDA), other times it may mean continual blooming conditions until the trigger is removed.

I think we must also recognize that many of the species of algae we deal with in our aquariums have been taken out of their environmental contexts. These algae species have hitched rides from every corner of the globe so particular blooming conditions (like low phosphate levels for green spot algae [GSA]) might be particularly adventitious in the alga's native habitat due to a specific predator, competitor, window of opportunity etc... and now it is not so easy to determine what benefit the algae is getting from blooming in response to the trigger. The relevance of the trigger to the alga's survival has become lost in our home aquarium, but the blooming conditions have not (yet?) changed.

What I would truly find interesting is to find out the original environmental situation of a species of algae that constantly grows in conditions within the recommended range (10-20 ppm nitrate, etc...). I would bet that if such an alga existed that it would occur in water absent of aquatic plants.

*As a point of interest:*
With a bit of research and the help of an algae specialist I managed to track down the original environment type for Cladophora. Claudophora is native to fast moving stream environments that do not harbor aquatic plants in the water column but rather only on the bank where the plants do not compete with algae for the niche. Given this algae's evolutionary niche with no competing aquatic plants it makes sense that it is programmed to constantly grow if there are nutrients in the water since it has not had to compete for nutrients or light with aquatic plants like other kinds of algae.

*In marine environments:*
To further my hypothesis I would like to bring attention to marine algae. As any reefer knows having the most minute concentration of nitrates or phosphates causes algae growth. In the presence of nutrients usually some kind of hair algae takes over and wrecks havoc on every surface of their tank. I believe that this algae, like the clado, has evolved to grow at a constant pace if there are nutrients present since it has not had to fight for nutrients and light with aquatic plants. In fact, there are very few aquatic plants in the world that are able to live in the ocean like algae, and corals grow far too slowly to out compete the algae for nutrients and light. Therefore a majority of the algae species living in the ocean should grow at constant rates when nutrients are present and this is exactly what we see in real life. For example: kelp, macro algae, micro algae, diatoms floating about in the water column etc... all grow at constant rates when there are nutrients present, they do not go dormant and then spring to life en mass like in freshwater tanks. Naturally there are blooms of algae in the sea, but this is simple because the existing algae that has been growing just fine has been given a bigger stock of nutrients from which to grow. The extra nutrients are simply able to support more algae that has already been growing at constant rates all along in lower quantities.

*In summation:*
The majority of algae in our tanks are opportunistic bloomers because if they grew all the time, plants would out-compete them for nutrients and light and they would go extinct. To survive they lie dormant in some form until conditions signal them to grow for a short period of time and then return to dormancy.

*Thoughts:*
I want to invite people to comment on this idea and hopefully we can get a discussion going about it. Perhaps at the end of it we will understand the delicate balance between a beautiful aquatic paradise and an algae nightmare instead of chalking up all our success to


> if you address the needs of the plants, algae problems "magically" go away.


 (Thanks BryceM! )


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## davemonkey (Mar 29, 2008)

Zapins, that's a wonderful observation and explanation. I don't have much to add in the way of good discussion, but reading through your explanations I realized a few things in my own tank.

Over the past 3 months, I've had nearly every algae you can imagine at one point or another, and I've changed nutrient dosing in every way/combination, and end up 'controlling' one algae while getting a bloom of another.

I have a hunch now, that if I just stick to a good routine, the algae will go through it's cycle and return to dormancy. My main problem is a lack of patience, I believe. I've been making too many adjustments too quickly.

Any thoughts on that?

-Dave


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## Zapins (Jul 28, 2004)

I agree, try keep the nutrients consistent, and try dose nutrients within the "golden plant range" (5-20 ppm NO3, 2 ppm PO4 etc...) for 2 weeks or so until the algae bloom finishes. Things should settle down soon!


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## BryceM (Nov 6, 2005)

Nice stuff Zapins.

I think my own understanding of this is to the point that I can make a few fairly solid comments:

1. I agree that stressed plants take a long time to recover once favorable conditions return. Depending on the species and setup, this can take 2-6 weeks.

2. The notion that a measurable level of macronutrients in a planted tank will lead to algae issues is not a correct one. (This was actually the basis of a recent article in TFH).

3. The growth phase of algae is multi-factorial, and simple availability of what algae need is not sufficient to lead to nuisance levels of algae.

4. Not all aquariums are created equal. What works in one situation will not always be appropriate in another. There are exceptions. Green water always dies with UV, etc.

5. There is an relationship between light intensity and the precision required of a person to keep conditions steady.

6. Algae are smarter than us. They are also more patient.

7. No matter what, you will encounter algae issues from time to time. It is like a chronic medical condition that can never be cured, but does respond to careful management.

8. When in doubt, work to meet the needs of the plants.

9. When things go bad, look to yourself first. Don't skip dosing, be careful with your math when mixing solutions, keep filters cleaned, etc. Slacking off on my fertilization and maintenance program has been the real issue with many of my own algae battles.


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## Bert H (Mar 2, 2004)

Good discussion here, and real nice write up Zappins! I will echo what others have said in that consistency and patience are of utmost importance. 

I recently switched water sources on my 10 gal going from my well water liquid rock (kh11), to my son's city water with kh 3-4 as an experiment to see if I could grow some of the plants I'd always failed miserably with (R. macranda). Before the switch, the tank was what I called algae free, which meant gsa on the glass, but otherwise clean. After the switch, which occurred about 6 weeks ago, the gsa has pretty much disappeared, but I have what looks like a staghorn/hair algae cross sprouting all over the tank. I'm hoping time, consistency and the Amanos I'm about to put in there, will return things to a clean state. But even with the algae outbreak, the plants continue growing at a normal rate.


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## ashappard (Jun 3, 2006)

good no-nonsense list Bryce.

If I notice any magic to a tank with an algae free appearance, its that the algae cant tolerate disruption 
as much as plants. If I neglect a corner of a tank, or don't keep sediment off the leaves, etc. any 
lack of good husbandry - the algae will take advantage of this and then I have work to do cleaning it up.

If I pester the algae, pull it off leaves, alter flow, swish around sediments and then change water for example; 
It stops blooming and suffers, where nutrient levels stay the same and the plants are still doing well.



BryceM said:


> Nice stuff Zapins.
> 
> I think my own understanding of this is to the point that I can make a few fairly solid comments:
> 
> ...


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## tonbrencat (Jan 21, 2009)

Great write-up on algae-I understand it much better-Thanks


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## Zapins (Jul 28, 2004)

Thanks everyone for the comments so far on my idea. 

I am specifically interested in starting a discussing of the idea's shortcomings rather than discussing some of the old generalizations up until this point. At the end of the discussion (if there is an end) I want to piece together a better theoretical understanding of what makes algae grow in our tanks rather than a nonspecific list of generalizations. Potentially something that could be tested for or surveyed.

In particular:
1) Did you read the entire article?
2) Are there any glaringly obvious flaws with the idea I proposed - if so, please outline them clearly and give evidence of some kind.
3) Are my examples sound? Did I generalize too much or not enough?
4) What do you think of the idea itself? Does it seem to make sense? 
5) If I, or someone else were to make an actual experiment to test part of the idea what would it be? Surveys of wild habitat? Algae + fertilizer tests? Specify as much as possible.
6) If anyone knows the origins of any specific type of algae, or where it does best in the wild (I.e. with aquatic plants, or in lakes with no plants, lakes with ponds, streams, etc...)
7) To a lesser extend, I would like to know if there are any personal experiences you have had that either match the concepts put forth here or go against them. Explain as much as possible.
8) Anything else that is relevant to understanding algae better.


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## Fishtory (Jan 21, 2009)

Hi Zapins,

It seems to me that if you were to test, you would need to do so in an aquarium, not in the wild -- as that is what we are interested in on the forum. 

The testing would have to hold all points constant except the one being tested; i.e., the trigger you are trying to create. So the pH, kH, etc. should be noted and should be the same across the board as you try to recreate the triggers.

Just my 2 cents.


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## ShaneSmith (Feb 15, 2004)

Zapins, excellent stuff here. I actually explained the EI method to a couple of professors here at UF. One suggested allelopathy might be the reason, the other suggested that the algae may only bloom when it 'senses' low nutrients. He suggested the algae evolved to rapidly multiply and reproduce when it senses bad conditions to ensure survival (Spores maybe he didn't know what type of algae i was talking about).

In particular:
1) Are there any glaringly obvious flaws with the idea I proposed - if so, please outline them clearly and give evidence of some kind.
Well i don't think the focus should solely be on lack of nutrients that causes the bloom. Maybe type of nutrient. NH4 is much preferred by algae so maybe as soon as a 'dormant' cell get a sip of NH4 is reproduces. Best evidence i have is that when i leave old leaves to rot in my tank i immediately get algae growth (OM breaking down, not enough for a 'bloom' but noticable increase). After all its not a very good idea to rely on blooming when there is not much material to bloom with (I know they don't need much but its just a thought).

2) Are my examples sound? Did I generalize too much or not enough?
- I'll admit i didn't read the whole thing, i am taking a break in the library. I thought it was an excellent evaulation though.

3) What do you think of the idea itself? Does it seem to make sense? 
Yes it makes sense BUT, obviously this subject is going to be more complicated because each algae is a totally different organism. Their evolution might not coincide. Nobody is going to pay a scientist enough for him to figure this out so assumptions are our best bet i think.

4) If I, or someone else were to make an actual experiment to test part of the idea what would it be? Surveys of wild habitat? Algae + fertilizer tests? Specify as much as possible.
I don't think natural bodies of water are applicable. To bring a lake up to 20ppm nitrate would be absurd... the amount of nitrate would be enormous. What we have to realize is plants grow on the banks and shallows of lakes. The majority of most lakes do not have plants or algae in the center (Majority of volume). .00001 PPM nitrate is still a massive amount, the plant mass needed to utilize that is most likely not in the lake. Concentration gradients are going to bring the ions to the plant so the plant will never run out of nutrients even if the lake has low concentrations. This needs to be done with aquariums. I might have time to work out an experiment later but honestly thats a lot of writing and its kind of complicated. I would probably need help from a PhD.

6) To a lesser extend, I would like to know if there are any personal experiences you have had that either match the concepts put forth here or go against them. Explain as much as possible.
I have observed a drastic reduction in pearling when nitrite is present in a tank (no other changes). the plants are not photosynthesizing and this could cause algae problems. Cause of nitrite spike could have been over feeding in a newly cycled tank. I had some births and was over feeding to try to keep the parents from eating the babies. THis has occured 3 times now, when i see plants reduce pearling i test for nitrite and everytime its there. 4 days later nitrite 0 plants blinged out.

Great stuff man.


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## Supercoley1 (May 28, 2007)

I'm not pooh poohing after all we are all here to have beautiful tanks and therefore discussion on these subjects is something to be welcomed, however......

I pretty much agree with Bryce (apart from the 2ppm of PO4 as I dose 5ppm )

I have no algae in my tank yet I dose full EI under what you guys would call low light (pre LEDs that I put in a few weeks ago I had T5HO - 0.9WPG for the 9 hour period with a noon burst of an extra 0.5WPG.)

I do not vacuum the substrate. I empty the water from the filter hoses.

I do not clean leaves.

I do not clean up used food, I leave it!!!

I used to have various algae problems. Then I changed 1 thing and haven't seen algae since!!!

I added a Koralia1 which bumped my flow from 5.6x to 17.6x turnover per hour!!!

So my conclusion (which may be wrong ) is that flow was the cure. Not just cleaning plants and keeping detritus in suspension but also circulating nutrients better and more importantly improving CO2 circulation!!!

I have some fern leaves that are disintegrating after being damaged yet there is no algae present. There are a couple of damaged leaves that look like madagascar lace plants but still no algae on the 'wound'. I haven't trimmed them because I want to see how far they will disintegrate without triggering algae but so far it looks like they may just fall apart with no algae!!!

AC


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## ShaneSmith (Feb 15, 2004)

Maybe that is a function of the low light? Could you tell me the time from of start-up to algae to adding the koralia and fix of algae problems?


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## BryceM (Nov 6, 2005)

Zapins,

My only hesitation here is that we shouldn't over-simplify the question. We're naive if we think that the different forms of algae respond to identical mechanisms. In some planted-tank circles, people even exchange algae to try to inoculate their aquariums with algae that is less prone to be a nuisance.

The more I play around with aquariums, the more fascinated I am at the complex interactions that take place with these unbelievably simple, yet complex, single-cell organisms.

I'm nursing a couple of "pet" theories. Maybe they could be incorporated into any experiments that you can design. One is that healthy plants have an ability to "fight off" algae "infections". Plants don't have a classic immune system in the same sense as vertebrate animals, but they do possess some pretty solid innate immunity systems. These systems would probably apply more to BBA type algae, which often invade the actual plant tissue. Old, sick leaves are the first to be affected IME.

Diatoms and thread, OTOH, tend to just coat the surfaces of the plants.

Complex stuff.......


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## Supercoley1 (May 28, 2007)

I won't go on about the light. What I am implying is I am dosing Full EI (supposedly for medium to highlight tanks and CO2) so there is more than excess if it is indeed low light.

The scape was set up in July 2008. It was algae free at the beginning and was lean dosed. The flow at this time was 5.6x using just the filter so in reality allowing for flow restrictions 50% x 700lph = 350lph / 125Ltr = 2.8x

The algae started when the plantmass got larger and larger (the sig pic is the scape in question) and there were all the usual suspects there (rhizo, clado, BBA, GSA, GDA.)

As the plantmass grew the flow reduced as plants become barriers to the flow. This meant CO2 was not so good either and I was getting a dark green DC when it had been almost yellow from the beginning. I ended up at 5bps to get to mid green whereas it was on 2bps before the algae war

I tried several combinations including using a tradition 400lph powerhead trying to sort the problem but eventually gave in and bought a Koralia 1 (150lph with minimal flow restrictions) in Mid December.

This managed to get the CO2 into the yellow on both DCs with the improved circulation. I ended up back at 2bps and getting a nice lime green almost yellow 

Algae was virtually gone within a couple of weeks.

S since having the Koralia in there for nearly 2 months now I have no algae apart from a few leftover blobs of GSA on Anubias leaves. If plants do get damaged and deteriorate I no longer get algae on the damage which I had always believed was inevitable (ammonia leeching = algae at source.) This has proved that it isn't the case unless I have a magic fern :lol:

I haven't cleaned the glass for many a moon. I don't get GDA/GSA on theglass. I let it go through a 4 week cycle at the beginning and it never returned!!!

AC


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## houseofcards (Feb 16, 2005)

Let’s get back to general algae talk and not what’s happening in one person’s tank. I agree that “addressing the needs of the plants” is just one part of the equation. 

There are very few guaranteed solutions IMO to algae issues in each person’s tank since every tank has so many different variables it would be difficult if not possible to analysis the effect each one has on each other and the alga that results. Many times in the threads there are scientific solutions offered to one’s algae issues which end up solving nothing or possibly making the algae worse. Trying to pinpoint someone’s algae issues is sometimes like playing pin the tail on the donkey. 

That being said, I do believe there is a direct and dare I say indisputable relationship between organic control, light and algae. 

I like to use the example of a swimming pool since it seems to be straightforward.
A pool sits outside in massive amounts of light. We dump chlorine in the pool to kill any organic matter. Without chlorine the pool would quickly fill with algae. The more sunlight the pool receives the quicker and more profound the algae is. This combination of water, light and organics exists in our tanks as well. Unfortunately our tanks are more complex and we can’t simply dump chlorine in to control algae, but without a doubt there are parallels. 

In the tank the bio-filter, organic filtering products and the ability to adjust light duration takes the place of the chlorine. Organic control is a very broad term. Healthy plants, bio-media, carbon, products like Purigen all are subsets of organic control. As well as limiting food, fauna and the removal of dead leaves from plants since they all either remove or add to the organic levels in one’s tank. 

Most algae issues take place soon after startup. At startup the ability to control organics is challenging since you don’t have a mature bio-filter in terms of plants and media. To fill this void carbon, purigen, seeded media and water changes are used in tandem with a reduced light duration. I have started up many tanks this way and have never had a nuisance algae issue if these steps are followed:

Seeded bio-media
Carbon/Purgien
Light duration ~ 6hrs.
No livestock 1st month
Remove any decaying plant matter
Weekly 50% water changes
Large Plant mass fertilized as needed

If the tank is high light and/or limited plant mass (iwagumi) it is even more important to follow each and every one these religiously to avoid issues. Once the plant mass starts to grow and the bio-colony expands some of these can be relaxed like the removal of carbon and increasing the light duration. IMO healthy growing plants help control algae, but they are only a part of the organic control process. I don’t pretend to know the levels and/or reasons why an algae bloom might get triggered. I think this would be almost impossible going back to my opening paragraph. But I do know when I apply the steps above to my tanks, I do not get algae. Predicting what triggers an algae bloom, IMO is like predicting the stock market. There are just too many variables to consider. This is where experience comes in.


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## nfrank (Jan 29, 2005)

let me throw in 2 other variables -- O2 and CO2 levels. More as a hypothesis and not a firm conclusion.

When tank plants are pearling, O2 is saturated. Algae is often not present. Does the algae find it harder to develop because the plants are healthy and are sucking/storing nutrients making them unavailable to algae in the water column (assisted by good water flow)... and there aren't any dead leaves to leak nutrients... or does the high O2 by itself somehow inhibit algae (say, analagous to H2O2 treatment)? The algae limited nutrients under good plant growth could be one of the traces, particularly if N, P, and K are maintained at high levels. Such nutrients may only need to be limited for short periods, not all the time.
Also, does 30+ppm CO2 in some closed planted aquaria situations also inhibit algae, again when there is sufficient flow to keep it well mixed in the water column. In fact, the combination of CO2 and O2 may also be a factor, something that is not typically found in nature; particularly in fast moving streams where O2 but not CO2 can be high.
These are purely speculations and not something i have seen in the literature....throwing it out for reaction.
--Neil


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## houseofcards (Feb 16, 2005)

High co2 levels to me play a part as will proper dosing since they drive plant growth thus in turn help with organic control, but in itself I don't believe high co2 will prevent algae issues. I have seen tanks with ridiculous co2 levels and they still have algae.


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## ShaneSmith (Feb 15, 2004)

I think that so far we have three good idea's going

1. Lack of nutrients cause algae to bloom as a responce to try to expand to higher nutrient areas. or to survive the low nutrient levels by sheer numbers.

2. NH4 released by organics breaking down causes algae blooms. THink of it this way. The nitrifying bacteria are on surfaces... so rotting organic matter releases and NH4 either the NH4 makes it close to a surface and is affected by bacteria, or an algae strand hits it. the organics slow release this nh4 so there may be just enough NH4 that the algae reproduces very slowly and is manageable most of the time. However when something disrupts the bacteria just a little bit the algae gets enough of a cencentration of NH4 to bloom. Algae can also use NO3, but not as readily i dont want to confuse anything. 
---About the tank with low light, rotting organics and low algae. I believe there needs to be a certain threshold of light also for the algae to bloom. Sunlight is much brighter than the brightest t5 HO or VHO set-up.

3. Allelopathy which i can't personally make much sense out of. unless the chemicals have a very shor half-life, they would build up in the water.


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## DonaldmBoyer (Aug 18, 2005)

One could add the perfect algae removing device to their tank, and unless the tank is located within a purfied and sterilized vacuum, algae will always be in the water. As they are on the microscopic level, they are able to ride air currents; in fact, you are inhaling them as you read this. I think that this needs to be understood for the "novice" who may be reading this. You will NEVER get rid of algae in your tank, and I believe that this article really concentrates on prevention. Even those who are fortunate enough to not have GSA on their glass or mounds of clado growing they can always get it if a parameter of prevention is not followed or one gets too comfortable and follow the routines associated with prevention. It is very difficult to get rid of all organic decay in a tank, but if all other parameters of prevention are followed, one shouldn't need to rid their tank of ALL decay rather just most of it. It is when a combination of key guidelines are not followed do the environmental conditions become favorable for an algal bloom or growth. The aquarium water could be completely sterile of algae and hypothetically speaking, so could all of the plants, wood, substrate, etc., but algae will always be present in the tank.


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## simpsota (Mar 11, 2006)

Supercoley1 said:


> So my conclusion (which may be wrong ) is that flow was the cure. Not just cleaning plants and keeping detritus in suspension but also circulating nutrients better and more importantly improving CO2 circulation!!!
> AC


I am not an expert and would love to find the best technique to keep algae minimized at all times. However, I would agree with the observation that flow is an important parameter.

I have an XP3 on my 50g and recently noticed that the flow was getting severely reduced due to fouling but I didn't have time to clean the filter. At the same time I also noticed a large increase in algae and little to no pearling even though my CO2 drop checker said there was plenty of CO2 around. I finally got around to cleaning the filter out and there is now so much pearling that even the tank walls are coated with bubbles. Improved flow was the only change. So I'd say that good water flow is a variable to keep in mind with any designed experiment.

Those out there who are familiar with mass transfer film theory will say that with poor bulk water flow the film thickness on leaf surfaces increases reducing the rate at which nutrients can be absorbed by the plant, even if they are readily available in the water column. Just because a nutrient is in the water doesn't mean a plant can use it. It has to get to the plant's cell membrane before it can ever be absorbed.

So maybe it's not just a lack or excess of a nutrient(s) that could cause an algae problem, but also a lack of availability to the plants that can cause a problem. This would include cases where poor water flow past the plant surface leads to a localized lack of availability. If the flow gets too bad large portions of the plant population could be having difficulty getting to the nutrients causing them to suffer and allowing excess to exist in the water column for algae to take advantage of.

I don't think good flow is a magic cure all, there have been several good ideas presented so far in this thread, but I think good water flow is probably important enough to be kept on the list of variables to check, or at least monitor. As one experiment, it would be interesting to run two tanks with the same set-up and nutrient concentrations in the bulk water and have one with vigorous flow and one with very limited flow to see where and how much algae grows in each.

Of course now that I think about it, which was the bigger impact to algae production, significantly increasing the bulk water flow throughout the tank or removing a lot of detritus from the filter media? I think the improved flow was likely the cause of improved pearling, but was that also the direct or indirect cause of a reduction in algae growth???


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## Fishtory (Jan 21, 2009)

simpsota said:


> Of course now that I think about it, which was the bigger impact to algae production, significantly increasing the bulk water flow throughout the tank or removing a lot of detritus from the filter media? I think the improved flow was likely the cause of improved pearling, but was that also the direct or indirect cause of a reduction in algae growth???


I have algae for the first time in a million years, despite setup/takedown of many different aquariums during that time. The 2 algae-infested tanks I have now are my 2 [new to me] planted tanks, so I'm particularly interested in the answer to simpsota's question.

Also, what constitutes an acceptable flow rate? And now that I'm faced with plants, which block the filter uptake somewhat, should I be stirring or water changing more frequently in order to reduce the algae? Not trying to hijack the thread here, but you are all talking about "good" flow and I'm not sure of the definition.

This was all much simpler in fish-only tanks!


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## houseofcards (Feb 16, 2005)

I think your getting away from the idea of the thread. Flow in itself is not going to trigger an algae outbreak. Flow might be a factor if you believe the plants aren't getting what they need to grow strong enough for your tank's conditions. So in turn the plants aren't utilizing the nutrients in the water and then possibly because of the increased nutrients you get an algae outbreak. I don't believe there is any magic bullet for flow. EVERY tank is different. I could show you tanks with no flow (no filter) and they are spotless and I could show you whirlpools and there is algae.


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## Zapins (Jul 28, 2004)

*Shane*,
I explained EI to my professors too and they also mentioned allelopathy. However, they thought it might also be nutrient related. One of the courses I took dealt with algae in particular, and there were apparently several studies done on lakes where they tested the water at different times of the year to see what bloomed for several years, what they found was certain species of algae bloomed at different times of the year. The algae blooms seemed to depend on environmental cues like nutrients and day length to initiate a bloom. Building on this research I think we could do something similar with aquariums and get some really interesting results.



ShaneSmith said:


> 1)&#8230;Well i don't think the focus should solely be on lack of nutrients that causes the bloom.


I think there are probably lots of things contributing to algae growth, but I think it is best to look at only a small set of possibilities that causes algae instead of everything. Since my theory centers around algae being caused by nutrient levels being out of a "golden range" I'd like to focus mainly on nutrient levels and testing which ones cause blooms. I would very much like to test NH4 in some way though because after all N is the most used nutrient by plants and algae and NH4 is the preferred nutrient (like you mentioned).

Perhaps no bona fide scientist will get hired to do the research for us, but we could probably get some meaningful tests going! Some of the most important scientific experiments where done with next to nothing in terms of fancy equipment, just good old fashioned planning and dedication.

I agree that lakes probably aren't the same as most people's tanks, primarily because the nutrients come from soil. I did a few tests on several bodies of water over the years and I also found 0-0-0-0 levels of all testable nutrients. I'm curious to know what experiment you are thinking of. I think it could be very interesting.

Interesting that you got pearling with low nitrates, this might be why I haven't seen my plants pearl in a while. Have you read my post on gluteraldehyde and how it might help plants absorb nitrogen? I'm still waiting for my chemistry teacher to email me back on that, but nonetheless it might provide some other background reading 



BryceM said:


> Zapins, My only hesitation here is that we shouldn't over-simplify the question. We're naive if we think that the different forms of algae respond to identical mechanisms. In some planted-tank circles, people even exchange algae to try to inoculate their aquariums with algae that is less prone to be a nuisance.
> 
> I'm nursing a couple of "pet" theories. Maybe they could be incorporated into any experiments that you can design. One is that healthy plants have an ability to "fight off" algae "infections". Plants don't have a classic immune system in the same sense as vertebrate animals, but they do possess some pretty solid innate immunity systems. These systems would probably apply more to BBA type algae, which often invade the actual plant tissue. Old, sick leaves are the first to be affected IME.


*BryceM*,
I am curious how a plant's immune systems are able to fight off surface algae. I think this idea has a lot of merit especially with fighting off algae like BBA, green spot/green dust algae. How would their immune systems prevent algae from growing on non-plant surfaces in the tank though? Allelopathy? How would that be tested for? Also, I think it might be interesting to find out why it is old leaves that grow algae vs. new leaves.

Also, I agree there are probably many factors that determine how badly algae affects a tank, but in order to figure out any of them it will be necessary to ignore most of them and specifically examine only a few factors at one time. I think nutrient levels have a lot to do with initial blooms (lake studies at different times of the year - see above). After the bloom has initiated then plant defenses probably have a lot to do with keeping them healthy and free of the epiphytic algae. At each phase of an algae bloom I see the potential for "nipping the problem in the bud" so to speak. We just need to find out how much each factor affects algae.

I think since the theory centers around the idea that there is a nutrient range that prevents algae growth from being triggered that we should first look at each of these conditions and then go on to the more obscure and difficult to control variables (allelopathy, O2, organics).

In addition to Shane's list of general ideas so far here are some other things to consider:

1) Why do new tanks have start up algae? Is it because nutrient levels are out of whack or is it because of something else? Is it possible to start a tank up without algae problems? If so how and why?

2) What role do bacteria play in algae? Doing some experiments with a broad spectrum antibiotic (fish medication) might help clarify just how much of a role bacteria has in either suppressing algae or causing it. It would also show the differences between new tank setups that have less bacteria and old tank setups that have more bacteria.

3) Test what types of algae occur with changes in what type of nutrient. Done by changing one nutrient level at a time: the first tests starting with nitrogen levels (NH4 vs NO3), then phosphate, Iron, CO2, Calcium, Magnesium, etc&#8230;


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## Zapins (Jul 28, 2004)

I just wanted to add a few things.
First, I would also like to let people know that what I am asking is not so much "how do we find the ultimate rule that will eliminate algae forever from our tanks for everyone" but rather simply _understanding_ why algae happens. I think if we have a good understanding of why algae grows, what causes it, its interactions with other variables in the fish tank then each and every person can look at the big picture and figure out where their problem falls on the map and take a course of action that will solve the problem specifically for them. I don't think there is 1 method that will gaurantee algae free tanks forever, but I solidly believe that there are very real reasons that cause algae and that these reasons affect everyone equally. The responses that algae species have to their environment are encoded in their DNA, which is relatively uniform across people's tanks (since we all trade plants). These genes are triggered in response to specific environmental cues in each of our aquariums. There are probably many factors that trigger the same DNA and the same algae behavior, so the goal is to find out what triggers what growth behavior. What we find may not be 100% of the picture, but at least it is a start in the right direction and will undoubtedly lead to actual results that we can use to prevent algae growth and suppress it once it has started.

Second, I would like to thank houseofcards for keeping the discussion on track. While one person's experiences are useful in getting an idea of problem areas that could be researched they aren't very useful when it comes to understanding what is going on at the root of the problem. I think this goes back to what BryceM said in his first post about "what works for 1 person doesn't work for everyone."

Finally, I want to thank DonaldmBoyer for reminding everyone that algae will never be eliminated, but it can certainly be _prevented_. It is important that people new to the discussion have a clear idea of what is going on and what is being discussed and proposed.

I think the discussion so far is going very well - much better than I had expected and I want to encourage everyone to keep posting ideas and thoughts!


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## BryceM (Nov 6, 2005)

simpsota said:


> I finally got around to cleaning the filter out and there is now so much pearling that even the tank walls are coated with bubbles. Improved flow was the only change.


No, you also removed an enormous amount of organic material from the system by cleaning the filter. That might also have had a beneficial effect. I think good flow is important to any algae eradication strategy, but it isn't the whole story.



Zapins said:


> I think since the theory centers around the idea that there is a nutrient range that prevents algae growth from being triggered that we should first look at each of these conditions and then go on to the more obscure and difficult to control variables (allelopathy, O2, organics).


The day-to-day consistency of water column nutrients might be more important than their actual concentration.



Zapins said:


> 3) Test what types of algae occur with changes in what type of nutrient. Done by changing one nutrient level at a time: the first tests starting with nitrogen levels (NH4 vs NO3), then phosphate, Iron, CO2, Calcium, Magnesium, etc&#8230;


So far, the prevailing wisdom on this point is that NH4 causes BBA, a high PO4 to NO3 ratio results in thread algae, high Fe can cause thread algae, and low nitrogen levels with poor circulation causes BGA.


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## Zapins (Jul 28, 2004)

BryceM said:


> The day-to-day consistency of water column nutrients might be more important than their actual concentration.


I think so too. But I think there is a bit of leeway involved in keeping the concentrations consistent (e.g. 5-20 ppm NO3), this is what I meant by "golden range."



BryceM said:


> So far, the prevailing wisdom on this point is that NH4 causes BBA, a high PO4 to NO3 ratio results in thread algae, high Fe can cause thread algae, and low nitrogen levels with poor circulation causes BGA.


Good info BryceM!

Does anyone else have any more info like this?

I know that Green water can also be triggered with high NH4 levels and strong light, and green spot algae seems to occur when there are low phosphates.

*For example:* 
1) Will high NO3 cause BBA instead of high NH4? 
2) What ratio of PO4 to NO3 causes thread algae? 
3) How much iron triggers thread algae? 
4) What NO3 levels will trigger BGA (these guys are interesting because they can nitrogen fix from the atmosphere and are bacteria)?

These kinds of generalizations are useful because we can test for them in different ways and see what other conditions can trigger the same type of algae, BryceM says Fe and NO3/PO4 can trigger thread algae, the next question is what combination of these nutrients triggers them? Is it repeatable? If we know what combos trigger it then we can avoid them and not get hair algae.


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## ShaneSmith (Feb 15, 2004)

We're going to have to do this one variable at a time. Zapins if you want to test the theory that a range of nutrients needs to be maintained to keep blooms at bay then i think a three tank trail should be done. I'll write out my idea of how we might do this, i have never done an experiment on my own before so input is appreciated.

3 tanks all from same tap water source, same size, same light, etc... 

First tank
30ppm co2
No fish
Heavy plant load
Observe algae that grows or does not.
This will be a control, compare how a complete lack of nutrients affects algae

Second Tank
30ppm co2
No fish
Heavy plant load
EI Dosing
Again observe what grows

Third tank
30ppm co2
No fish
Heavy plant load
1/2 EI dosing
Observe the algaes

What we will hypothesize is that if the nutrients levels are lower than the levels maintained in EI dosing we will see algae blooms. Of course if the algae is comparable in all three tanks we reject the hypothesis and move on. If the algae is significantly less we fail to reject and move on to 1/2 EI, EI, and 2x EI. Etc...
Maintain 1/2 EI dosing

We will need to monitor NH4, NO3, CO2, pH. Optimally we should measure more things but 1 our test kits kind of suck, and two we're not producing a paper just trying to catch onto some trends.

Another option would be to start all tanks on EI and establish the tanks, the once the tanks are established and algae is considered 'dormant' We Increase dosing in one tank, maintain in another, and divide dosing by half in the third. Then observe what happens.


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## Zapins (Jul 28, 2004)

Shane,
I think it might be better to set up the tanks without plants initially because if the theory is correct algae should not grow if the nutrient levels are in a certain range - with or without plants. Having plants in the tank introduces other variables like allelopathy, faster changing concentrations of nutrients (plants are bigger & need more) etc...

What about starting with the recommended range of nutrients that people suggest? For example: 5-20 ppm NO3, 1-2 ppm PO4, 4:3 ratio of Ca:Mg, 30 ppm K, some traces (not sure how much). Initially we could set up little tubs or something under the same light and see if algae grows. One or two tubs would be the control (above) then we could change the nitrate levels and have a tub or two with 0 ppm, 5 ppm (everything else =), 10 ppm, 15 ppm, 20 pmm, 50 ppm. Then we can record what happens and which algae shows up and how much, and then go on to the next nutrient to be tested like NH4 and so on. To keep it simple no CO2 would be used initially, and for control ability distilled and reconstituted water should be used.

How would we inoculate the tanks though? Take a small 5 mL draught from our main tanks to seed the containers with all types of algae spores? Rely on air?


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## ShaneSmith (Feb 15, 2004)

Sounds like a great place to start accruing data.

I say we rely on air, spores are ubiquitous... they will find their way into the buckets!

I think adding co2 might be a good idea still, that will be a major limiting nutrient. I assume when we are talking about our tanks everyone is injecting co2... so why not include it? It will greatly increase the growth rates and if there are differences it will exacberate them.


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## Zapins (Jul 28, 2004)

True... CO2 would be more accurate since we all use it, but I am worried about 2 things. The first is how will we dose CO2 accurately? It is notoriously difficult to test for. I wonder if there are any good titration kits out there that we could use? The second is, how will we physically dose the CO2 into small containers (smaller than 2.5 gal tanks)? A diffuser or inline reactor might be difficult.

Also, I think you are onto something with letting algae seed itself in the tank. I think it might be cool to set up 2 experiments side by side, inoculate some tanks with water from another established tank and then run the same set of tests without the inoculation. I think seeding the tank with water would be helpful as well because a lot of the time algae spores come in on the plants we put in the tank initially and also it might be a while before algae spores from the air (especially with the dry winter air) get established.


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## nfrank (Jan 29, 2005)

houseofcards said:


> High co2 levels to me play a part as will proper dosing since they drive plant growth thus in turn help with organic control, but in itself I don't believe high co2 will prevent algae issues. I have seen tanks with ridiculous co2 levels and they still have algae.


i now realize that the thred is about how algae forms not its inhibition... but still would like feed back on my other theory: that high O2, at saturated levels may inhibit algae. The CO2 hypothesis was a secondary thought and not intended to be separate from already having very high O2.


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## Zapins (Jul 28, 2004)

I think the O2 idea is interesting. I think that it could have something to do with algae suppression and growth. I know from plant physiology that high CO2 or high O2 will inhibit growth of plants (because it overloads the enzymes responsible for fixing carbon), so I suspect the same would be true for algae. 

The research question associated with O2 and algae would be: perhaps algae's tolerance levels are lower than plants, so while plants can tolerate more CO2 and more O2 than algae the algae will be harmed by it and be inhibited. 

I suspect the inhibitory effects would be pretty small for most people and most species, since everyone usually keeps CO2 in a moderate range (levels below what would harm fish). But perhaps BBA has a very low tolerance for CO2 (in other words perhaps higher CO2 levels inhibit this plant's enzymes because it gas a less robust system than other algae).


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## Supercoley1 (May 28, 2007)

Where did BBA is cause by low NO4 come from? BBA is a classic symptom of unstable CO2 levels.

Try turning your CO2 up and down day to day and watch it grow!!! It is the bane of most yeast setups.

We can't go taking lake/river info for algae. Government scientists still claim that phosphate from farm fertilisation that gets into the water is the 'cause' of algae. The neglect to take into consideration that they forever disturb the silt, drag plants out of the water to 'make it clearer' etc.

In effect they are continually interfering with the water body by 'making it more sightly' and then saying fertilisers are causing the algae. If they had left the lake/river along, let the weeds/plants grow and not disturbed the silt beds then they would have some info to go by!!! Millions of pounds research to come up with a result that we can veto in an instant just by showing them that adding phosphate does not cause algae.

Algae benefits from the prescence of algae but throw in plants and all of a sudden as if by magic then the algae starts to disappear!!!

AC


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## Zapins (Jul 28, 2004)

You mean NH4 (ammonium) NO4 isn’t a possible chemical as far as I know. CO2 levels probably are also a trigger for BBA, like I said before, there are undoubtedly more than 1 factor that makes 1 type of algae bloom. 

I agree with you about the lake studies. They aren’t exactly the same as our tanks, but the results they found show what triggers a particular species of algae. If you consider that almost all nutrients in lake water are near 0 and our tanks are kept at much higher levels this might be why the algae was triggered in the lakes and not our tanks – because the nutrients in our tanks haven’t met the criteria for blooming (too high). We are in the “golden range” versus the lake nutrient levels. 

Perhaps if we made some experiments that kept all values as close to 0 as possible and just added 1 nutrient at a time it would give us an even better idea of what causes algae to bloom. If you think about it, algae might be acting exactly like plants with nutrients. If there is too much of 1 particular nutrient in the water plants will become inhibited (the excess nutrients block the uptake of other nutrients and deficiencies result). Perhaps algae are also inhibited in the same way, but with different ratios to plants. I think this might be a good thing to investigate. What do you all think?


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## Newt (Apr 1, 2004)

Having low NO3 will bring on BBA.
I lived that once....but never again.

High iron levels will cause BBA, too.


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## ShaneSmith (Feb 15, 2004)

Zapins,
If we want to say that X triggers a bloom in a high tech planted tank, shouldn't we try to imitate the environment we want to make the claim in?

We could still leave out plants and gravel etc.. but try to maintain the water paramters pretty close to start with. then add variables in later. let me know what you think

As far as the diffusion method, maybe buckets are a bad idea, 10-20 gallon tanks might be better. If the expense is too high the bucket method would still give us useful info


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## Zapins (Jul 28, 2004)

Shane, 
I think so too, I'm just not sure if adding CO2 to small tanks would be feasible but I think experiments without pressure CO2 would still be useful in shedding light on algae growth since CO2 really only accelerates growth. I think it would just take longer to get results without CO2. Come to think of it, does CO2 help algae grow faster? Or does it just help plants?

I'd love to get two sets of experiments going. One set would deal with keeping conditions like we keep in our tanks and the other set would have all 0 nutrients (distilled water or RO water) and 1 nutrient at a time would be added.


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## houseofcards (Feb 16, 2005)

Just for the record, I don't believe you can remove all of the organic content from a tank, but you do want to reduce it to a tolerable amount. What's tolerable? I really don't know, I don't think anyone does, but I do know when most people have algae issues it's after startup and this is when the tank doesn't have a mature biofilter to deal with all the organics. This isn't anything new, many professionals reduce lighting, use carbon/purigen, use seeded/filters to keep this at bay. I think to hit a bulls eye with this would be impossible, but to do all of these pro-active startup things it seems to target the problem pretty well. 

I think these tolerable ranges is what Zapin's is trying to figure out in terms of what triggers algae. Another thing to consider is that it seems a tank starts out unstable, then goes through a very stable phase and then as it matures (old tank syndrome?) issues arise. The startup to me anyway is pretty obvious (as discussed) why issues arise, but why do issues arise when the tank is older? Could it be during the stable phase the tank adjusts to it's parameters to a certain extent (ferts, light, co2, flow, etc.) and then when one of these parameters is changed simply because of one's lifestyle, maintenance schedule, etc. the tank can't adjust that quickly and the result is a trigger for algae. In other words, you could have two identical tanks and it's not really an issue whether co2 should be higher or lower just that it changed from it's stable period where the tank adjusted to the levels set. This would help explain why some people with seemingly similiar setups have different results when they try to adjust the same parameter. I guess it would be similiar to a sudden change in temperture from 78 to 72 and the result is fish getting ich as opposed to the tank that was always kept at 72 and none of the fish get ich. Parasites are many times present in aquaria but they are harmless unless triggered similar to the idea reiterated by Donald that the alga spores are always present as well, but who cares as long as their not triggered.


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## Supercoley1 (May 28, 2007)

I agree with house. We already 'virtually' know that localised ammonia and other organic nutrients are the trigger for algae. This is why many succesful scapers use Purigen, over filtration, high flow to remove as much organic as possible replacing it with inorganic. We can't get rid of all the organic nutrient but we can do our best 

The test doesn't need injected CO2. We inject CO2 to match the light given. I am talking unstable CO2 that cause BBA. 

Even in a non injected low light tank where someone does water changes this will arise because they are adding CO2 enriched tap water to the equation weekly. This is one reason why non CO2 tanks use the no water change method.

I'm not sure I agree with lakes having virtually zero nutrient either. Every water body in the world will have nutrients in it as a natural occurence. Ammonia is created from as simple things as dust particles.

My suggestion on low nitrates causing BBA would be that low nitrates causes many algaes because plants need nitrate more than all of the other nutrients. low nitrates may be OK for some plants which have low takeup rates but not for others where they have high takeup rates so you can be left with a tank where some plants do well, others dont, then you get the defficiency problems which leads us back to a healthy tank full of healthy plants doesn't get infested by algae!!!

AC


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## ShaneSmith (Feb 15, 2004)

Supercooley you read what i posted wrong. A lake will have a massive amount of nutrients even at low concentrations because of the sheer volume. 

I agree that was know ammonia causes a bloom, but it is a starting place to start establishing things. 'dust' could be many things organic or inorganic. 

Sunlight is much brigher than our tanks. if he was going to leave the buckets outside we would have to quadruple our co2 probably to keep up.

Tapwater is only enriched because air is compressed in the piping. It is probably nowhere near 30ppm.


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## Supercoley1 (May 28, 2007)

Forgive me for misreading your post.



ShaneSmith said:


> Sunlight is much brigher than our tanks. if he was going to leave the buckets outside we would have to quadruple our co2 probably to keep up.


People with outdoor ponds don't inject CO2 do they? I know someone who started EI on his pond and after a few weeks of good plant growth the algae disappeared!!! Maybe outdoors there is more CO2 than we think? or maybe pond plants (like lake plants) are more used to gainig CO2 by reaching for the surface?

I can find the link to that pond if anyone is interested. Another thing to add into the equation 

One thing I can throw in are a few questions for those who do suffer green glass (Gda) Does it only grow to a certain height in the tank? Is that your water change level? If so why do you think this occurs? Why does this algae only grow to the level where it is constantly exposed to the water?

Similarly on Anubias where GSA is a common problem, If you have any that are above the water level are they clear of GSA where the ones not exposed have GSA?

With both of these is it exposure to higher CO2 in the atmosphere that makes this difference? Is it exposure to high oxygen? Is there something else at work here?

AC

AC


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## Newt (Apr 1, 2004)

What do you prepose to stave off GDA and GSA? These are the only types I'm still struggling with. The GSA on the glass is half what it was but the GSA (lets call it plain green algae) grows on some of the plants: Older sword leaves, Java fern and a bit on the lower leaves of bacopa. I keep my macros at 10 ppm NO3, 1 ppm PO4 and 20 - 25 ppm K and CO2 (by the chart) is ~30 ppm. GH is 5 and KH 3


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## Supercoley1 (May 28, 2007)

doesn't sound like GSA growing on bacopa, sword leaves. GSA (green spot algae) normally grows on slow growing plants and is indicitive of low phosphates.

AC


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## BryceM (Nov 6, 2005)

I suspect that GSA grows on all plants. On rapidly growing stem plants the new growth "outruns" the algae and you never perceive it.


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## Newt (Apr 1, 2004)

Bryce, I think you are correct as it is only apparent on the older growth.

Any ideas on how to combat this? It is not a problem I have had until recently and I suppose I could look back thru my log and see what I changed.


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## davemonkey (Mar 29, 2008)

Newt, for what it's worth, I was able to greatly reduce GSA by upping phosphates. Although I can't say to what ppm (I don't test :loco: ) , I can tell you I use EI, and according to the fertilator, that should give me 2 or 3 x the phos that's recommended. (And I may be off on that number as well. )

-Dave


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## Newt (Apr 1, 2004)

Thanks Dave, I was going to up it from 1ppm to 2ppm slowly based on Supercoley1's post.

I like to test. I had an engineering teacher who always said "To test is to know".
I dont have the time to EI dose. I am one of those old school hobbists who 'ages' the water (for a week) and that would be too much time, too many jugs. I do PPS.


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## Newt (Apr 1, 2004)

I attached a word doc on an algae case study. I cant remember where I got it but was wondering what you guys/gals think of it. I have always reverted to 'starving off' algae problems by limiting phosphate and iron and waiting until it had died back and then re-balanced the nutrients in the water column.

Ooops....too big to attach so I'll copy and paste it in...............Ooops to big to paste in. I'll split the word doc into 2 parts.


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## Supercoley1 (May 28, 2007)

Those sort of tests are many and all well documented but they all come to the wrong conclusions in the end.

Think about it for a second. Plants need phosphates. They need much more than algae. Therefore to remove excess means to create a defficiency for the plants. Removing all nutrient wholly from the tanks will inhibit algae but it will also kill the plants  So in conclusion if you lower the phosphates whilst still providing enough for the plants then there will still be minute amounts of excess. Algae doesn't need as much nutrient as the 'higher' plants and therefore can feed off of much smaller amounts. 

Just getting a tank full of healthy plants will reduce the algae. I must be well over 5ppm phophate all the time. I dose twice the EI level and therefore will always have excess. I still get a little GSA on some of the Anubias but not much and is barely noticeable. I'm not sure that Cyanobacteria has much to do with phosphates but then I have never seen Cyanobacteria other than in pictures

The best limiting factor is light. limit the light and then it is easier to provide the plants with what they need than if you have highlight. The higher the light the more nutrient the plants need and the more circulation to deliver it better. Lower light tanks can sometimes get away with poorer flow.

So under the lower light (2WPG) it is much easier to keep CO2 levels up and nutrient levels up. Both in excess of the plants needs which are driven by the light. Allied with good flow these nutrients are delivered much better and then once the plants are growing well ALL algae recedes 

AC


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## Newt (Apr 1, 2004)

Thank you Supercoley1. I am in the process of slowly upping my PO4 from 1ppm to 2ppm in an attempt to get rid of my 'green' algae - the only one left.

Cyanobacteria is caused by heavily polluted tanks that are very high in PO4 and other excess nutrients and lighting that is strong in the 550 to 600 nm range where it peaks for phycocyanin absorbtion.










If you ever get BGA be very careful as it contains hepatotoxins that attack your liver.


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## Supercoley1 (May 28, 2007)

I've never heard about it being caused by light before? That is new to me. I understand it to be low nitrates and/or dirty filter/substrate etc. The 2 are sort of linked I suppose.

Where does this light part come from? Are there any papers on this one?

AC


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## Newt (Apr 1, 2004)

Not light alone but 600nm light along with a 'polluted' tank - high PO4, dirty substrate and filter. Blue-green algae (cyanobacteria) contain phycocyanin and absorb heavily in the 600nm range (yellow/orange). The Journal of Plant Physiology ran an article on it several years ago.


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