# Competition between plants and algae



## jerime

In many articles, both in the INTERNET and in aquarium literature, we see that plants and algae are battling for a given amount of nutrients.
the whole essence of fighting algae from the start is to limit the nutrients from the water column (where algae achieve it easily) and establish a good nutrient storage in the substrate where only the plants can benefit by it.
I often see posts here that advocate for increased fertilizing the water column for plants growth.
What would be the preferred way (if there is one). Why not using enriched substrate for the plants benefit while starving the algae by clearing as much nutrient as possible from the water column?


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## nino

Not all plants are heavy root feeders. Your idea would be fine if you only have swords and crypts in a low-medium light tank. But many fast growing stems pick up nutrients from water column.

You can only beat algae by using fast growing plants AND provide a condition for them to grow as fast as they can. Try to float some wisteria in your tank, you'll be surprise how fast they grow compared to when they're planted. IME, this is the best way to outcompete algae until the tank reaches its balance.


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## HeyPK

Another reason is that you can put nutrients in the substrate, but they don't stay there. They get into the water column by diffusion and by water movements.


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## freshreef

i also think that liquid ferts in the water column are better because u can control them easily - if u have more N or P or whatever - a simple w/c will help u to remove the access nutrient


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## plantbrain

Algae are more adapted to the water.
Algae are microphytes, plants are macrophytes, they exist in separate niches(they have different spatial and temporal scales, they are tiny, have much smaller nutrient requirements and need to respond much faster than weeds).

Heavy Plant growth supresses growth of algae by removing the NH4 fraction. This is a high energy rich nutrient that triggers a number of algal species.

You can prove this to yourself by taking a well run planted tank and adding either too many fish/food or adding NH4 in inorganic forms.

Then repeat the process with NO3. I never have been able in induce algae with higher levels of NO3, even 30-75ppm ranges at very high light.

Plants need far more nutrients in a planted tank than the algae, they have far more biomass.

Competition will occur only when the nutrients become limiting.
But algae will not grow unless given a certain set of conditions, they wait till there is a signal.

It might be temp, NH4, high light, CO2 variations(algae prefer CO2 like plants), high DO level durning the day(hey, someone else is growing there).

I've never bought the notion of allelopathy and it's never been proven in any research on aquatic plants in the field .....*ever*. Then it would have to exist and be the same for all 300 species of aquatic plants we kept as well and in every combination. What are the odds that this occurs?

No, I think it is much more an issue of the algae not growing in such a stable macrophyte dominated environment. Most aquatic ecosystems are geared towards change and submersed plants tend to have a stabilizing effect and need stability to do well.

So changes in CO2, NH4 cause the greatest effects, yes, there are more subtle effects but these are more difficult to see in terms of cause and effect.

Old literature did not take into account the PO4 locked up in the plants, vs the algae(see Phillips et al 1978), the Net had folks assuming ecological issues with out looking at competition.

Limnology seldom compared tropical or subtropical heavily plants shallow lakes full of weeds and algae.

Most research is bias to where the schools are. Generally in the north.

Florida is a great place for shallow lakes full of weeds. Ask any of the researchers there about this, and you'll get the same answer, adding PO4/NO3 to these systems will give you more weeds, not algae generally.

The water is gin clear(plants) or pea soup(algae).

It takes a long time to get a stable submersed weed population in many systems.

We come along and amplify this, we also select and remove algae, prune off old leaves, add lots of herbivores, provide stable places, feed for the plant's needs etc.

So the algae are very low in numbers in our tanks.

Myths and such get repeated and parroted.
The Net is great for that. But it can also solve things and disseminate. 
At face value some myths might even appear to make some sense.
But why isn't there more algae in planted systems in nature and in our tanks if this myth is true?

Why don't I have algae when I dose? Why do my plants grow so well when I add X nutrient?

Simply because a plant exist in a low nutrient water column and is able to use nutrients from the substrate doesn't mean it prefers that.

I think in the past many folks did a lot of assuming and very little actual testing to see what was going on. Then the other issue was test kits and confounding factors like limitations of NO3, K, PO4, CO2 etc.

Regards, 
Tom Barr


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## jerime

Well the basic idea here is to create the kind of substrate that will allow nutrients to stay in the substrate in the larger portion of it (high cec etc').

Anyway, the leaching problem is worse the the so called new method because we are now fertilizing from the start and we have some nutrients leaching from the substrate - bigger imbalance problem.
Regarding stem plants, if we clear the water column, they have no choice but getting their needs from the substrate. it's harder for them perhaps but also consuming nitrate instead of ammonia is hard, but still' we do not fertilize our aquarium with ammonia.
Again, wouldn't it be better to create a clear water column as possible instead of supplying both algae and plants with same ammunition?


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## jerime

Sorry Tom but I didn't see your post when I posted mine.
My question' regarding your answer' is: what are we to do when establishing a new tank : fertilize from day 1, thus enriching the already imbalance water or wait for a certain period till the plants acclimate and start consuming nutrients?
Wouldn't the method of supplying substrate instead of water column be better? does it have any affect at all?


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## plantbrain

No, you are gaining nothing by limiting the water column and selecting against the plants.

This does not hurt algae, they laugh at the levels we have. We have quite rich nutrients even if your kit says 0ppm. 

They operate at the ppb range.

Submersed Plants are limited at about 2.5X or more higher nutrient levels than periphyton(attached algae). 

Any fish waste, food, leeching will have a very profound effect on the nutrient levels for algae, while slowing the plants.

The entire notion of substrate dosing etc is to get away from regular water column dosing and one old arguement is that by having the nutrients in the substrate, you deprive the algae but select for the plants.

But that is simply not true, Algae are far from deprived or limited.

Also, adding NO3, PO4 etc to the water does not cuae algae blooms over a very wide range in well planted systems.
So what are you gaining?

Regarding NH4, aquatic plants(most terrestrials prefer NO3) and algae both like this one. But a small algal spore vs a large million celled plant
are at two completely different scales here.

One mole of NH4 means a lot to a small set of spores, while the plants might not gain much by this "free ride".

Plants also have the reserves to reduce the NO3 without much loss vs a small algae cell with little reserves at all.

Algae operate at this small scale and are able to get a jump on plants for the NH4 by growing on their leaves etc.
Algae do not need a lot, just a very small amount, plants need a hellva lot of nitrogen and we cannot add enough NH4 without algae and fish death so we add NO3.

There's a N article coming out in TAG so you can read about that more there.

Regards, 
Tom Barr


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## freshreef

great topic


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## aviel

Tom,

First of all thanks for this information - I can testify that once I started dosing ample kno3/po4/trace to my aquarium - algae is hard to find.

Still two things that I would like to yet understand better - 

1) Sounds like NH4 is a major contributor to algae breaks. With high fish load there's no longer need to add KNO3 since NO3 builds up. Fish add NH4 to the water and plants prefer that over the NO3 which builds up. But if Fish add more NH4 than plants can consume - then we are in a risk of algae break - right? So if I notice NO3 buildup then my tank if at risk - right? From your experience what should be the number of fish in a high light planted aquarium? 1 Inch per gallon - ok? More?

2) When there's an algae break - big break - is it possible for short term *(4-7 days) to stop adding nutrients, food, etc together with many water changes in order to make the water nutrient free? I mean algae don't have many reserves while plants do so for this short term treatment plants may win - no? I believe you recommend doing this for number one nutrient - light... if there's BGA and/or green water then you recommend a total blackout. So how about po4/kno3 "blackout"??? If plants just can't stand few days without those nutrients then how 'bout less demanding lower intensity for just a couple of days?

Thanks,

Aviel.

Aviel.


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## plantbrain

> 1) Sounds like NH4 is a major contributor to algae breaks. With high fish load there's no longer need to add KNO3 since NO3 builds up. Fish add NH4 to the water and plants prefer that over the NO3 which builds up. But if Fish add more NH4 than plants can consume - then we are in a risk of algae break - right? So if I notice NO3 buildup then my tank if at risk - right? From your experience what should be the number of fish in a high light planted aquarium? 1 Inch per gallon - ok? More?


A high fish load a small amount of NH4 will build up, enough to feed the algae and start a bloom.
It does not take much, a limitation, say low NO3, PO4, traxces, poor CO2 can cause a lull in NH4 uptake and thuis cause an algae bloom if you have a lot of fish.
More fish/feedings => more prone to algae.
Most plants you could argue prefer NH4 like algae, but in the scheme of things, the small trace amounts of NH4 present are much more important to algae.
They are far smaller and each molecule means significantly more to a single celled alga than a multibillion celled plant.

Algae are microphytes and not in the same niche as plants/macrophytes.

You may not be at risk if you see a NO3 build up, you might be limited by CO2, PO4 etc.
You might have a wet/dry and a fair amount of fish etc and the NH4 is still kept low.

I like 1" per gallon rule. You can add more, if the tank is run well.



> 2) When there's an algae break - big break - is it possible for short term *(4-7 days) to stop adding nutrients, food, etc together with many water changes in order to make the water nutrient free? I mean algae don't have many reserves while plants do so for this short term treatment plants may win - no? I believe you recommend doing this for number one nutrient - light... if there's BGA and/or green water then you recommend a total blackout. So how about po4/kno3 "blackout"??? If plants just can't stand few days without those nutrients then how 'bout less demanding lower intensity for just a couple of days?


Algae are triggered to bloom, they already have the nutrients and are gearing up for a bloom by this point.
Algae can go forever on next to nothing as far as nutrient levels. Some diatoms can last 100 generations on a loaded PO4 mother cell.
The math at the end of that is incredible at how little they need.

Water changes physically remove algae. It removed spores, young algae, prunign etc, fluffing the plants, cleaning equipment etc, herbivores etc.

Less light is better than anything.
You cannot blackout NO3/PO4, there's plenty in the tank as far as the algae are concerned.

This was the limitation theory that folks believed in before Steve and I messed with PO4. I was the observation, Steve did the first test.

Most plants can handle PO4 limitations for a few days without issue. NO3 can and will cause problems.

Neither of these nutrients help slow algae, but they will slow plant growth.
Light slows everything.

Regards, 
Tom Barr


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## aviel

> A high fish load a small amount of NH4 will build up, enough to feed the algae and start a bloom.
> It does not take much, a limitation, *say low NO3*, PO4, traxces, poor CO2 can cause a lull in NH4 uptake and thuis cause an algae bloom if you have a lot of fish.


I would like to better understand the "low NO3" limitation. In the case where there's high fish load NH4 is generated. Plants prefer NH4 and BTW therefore in this high fish load situation they flourish (right?). Plants won't use NO3 till they run out of NH4 so even if I have low NO3 - that's not a limitation. If I can maintain slow NO3 uptake then that would indicate that plants are consuming all the NH4 and need the extra little NO3. Now this could theoreticaly happend even if NO3 is as low as 2 ppm - plants just don't need it - right?

Of course that I have to have margins since after prunning NH4 uptake is poor which yes - could trigger algae outbreak.

Does this make sense?

Aviel.


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## plantbrain

Posted: Thu Oct 21, 2004 3:31 am Post subject:

--------------------------------------------------------------------------------



> I would like to better understand the "low NO3" limitation. In the case where there's high fish load NH4 is generated. Plants prefer NH4 and BTW therefore in this high fish load situation they flourish (right?).


It's a matter of total N, not the form when it comes to plant health.
Algae never have an issue with low N, whether it be either form, they will activate and bloom when there's enough NH4 present, once they activate, they will use NO3 as well.

When plants arer seriously N limited(NH4 or NO3), then they cannot take in NH4 very fast.

There is not a whiole lot of NH4 being produced in many tanks so to depend on this when the plant needs a lot N, is asking for trouble.

It could also be from low CO2, low PO4 etc that slows NH4 uptake down as well.

We do not know how much each person's bioload of fish is and how much they feed, this is a variable that is tough to gauge without some experience and/or rigorous test methods.
There are simple methoids to do this, but I'm not dicussing them in this thread.



> Plants won't use NO3 till they run out of NH4 so even if I have low NO3 - that's not a limitation.


No, the plant will begin to use NO3 when the plant is N limited, and it will also use any NH4 it can scavenage. There is simply not enough NH4 around to drive the plant's needs and there is an ample supply of NO3.
Suppression of NO3 uptake does occur when NH4 is offered, but there has to be enough NH4 offered, our tanks typically have extremely immeasurable amounts of NH4.
The system dynmaic between NH4/NO3 is *NOT* black and white.

Plants are already "blooming", like algae, once this occurs, they will use both NO3/Nh4 to grow and maintain their growth.



> If I can maintain slow NO3 uptake then that would indicate that plants are consuming all the NH4 and need the extra little NO3.
> 
> No, not at all, it could be low CO2, PO4, trace, decline in lighting etc.
> You'd have to rule out those first.
> 
> Typically, most planted CO2 enriched tasnks are set up to remove all the NH4 anyway.
> 
> Discus tanks may have up to about 50% of the N supplied as NH4 and little that gets converted to NO3 by bacteria I'd say.
> 
> As you add more light, the relative ratio(NH4O:NO3I) of fish waste(NH4) to inorganic NO3 N, becomes less.
> More light, faster growth, less.
> 
> Algae like high light and also NH4.
> You can push the limits in some cases but the overall stability is lessen as you go towards, more light and more NH4.
> 
> Many Discus folks change their water 2X a week, this removes NH4 build up. Some have even done daily water changes and this can allow this NH4 to added with somewhat decent results even if it's a PITA.
> 
> 
> 
> 
> Now this could theoreticaly happend even if NO3 is as low as 2 ppm - plants just don't need it - right?
> 
> 
> 
> Well, your test kit resolution tends not to be very good when you get down to the lower ranges. The kits also test total NO3, so it could be organically bound, rotifers/microscopic critters in the sample etc, not plant available NO3.
> 
> This is a good reason not to try and skirt the edge with test kits but rather *experience* and use the plants along with test kits, but doubt the test kits as a rule. Use them as a back up.
> 
> 
> 
> 
> Of course that I have to have margins since after prunning NH4 uptake is poor which yes - could trigger algae outbreak.
> Does this make sense?
> Aviel.
> 
> Click to expand...
> 
> NH4 uptake is related to biomass. So we do a large water change in conjuction, then we minimize this issue.
> If you do a lot of work on your tank, make sure to do this first, then do the large water change at the end.
> 
> My advice is in line with this going way back.
> 
> Regards,
> Tom Barr
Click to expand...


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## Bert H

Great thread folks!


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## aviel

Tom,

Thanks for taking the time to answer all my concerns -

My private problem is that recently my NO3 uptake went down to 0.7 ppm per day and it used to be 2.5 ppm per day. I measure NO3 using lamotte high range and it shows N=4 that doesn't change after a week of 0.7 ppm per day dosing. I tend to relate this to the fact that in the last month I added ~50 new fish to my 200 gallons tank.

Therefore I need to understand few more points:



> Isaid: If I can maintain slow NO3 uptake then that would indicate that plants are consuming all the NH4 and need the extra little NO3.
> 
> Tom said: No, not at all, it could be low CO2, PO4, trace, decline in lighting etc.
> You'd have to rule out those first.


Yes and I believe I ruled those out - I checked, double checked and tripple cheked my CO2 (KH=4, PH=6.5), PO4 = constant 1.5 ppm where I add 0.35 ppm daily, I also add 2 ppm K (through K2SO4) daily and iron at 0.25 ppm daily half of it from CSM where I get the traces from, light is 2-2.5 wpg so really - I don't see any limitation and still N won't drop significantly.

I think NH4 is generated and consumed immediately. Of course I can't measure it - one minute it's there and then it's gone -



> Typically, most planted CO2 enriched tasnks are set up to remove all the NH4 anyway.


I could never measure anything but 0 NH4 ever. But I thought that it's because tons of NH4 is generated and immediately being consumed by the plants. I thought that the N in the NH4 is now subtituting the missing 1.8 ppm (2.5 old NO3 minus 0.7 new NO3). Are you saying that total NH4 product is way below that?

If this is what you are saying then I have no idea what's going on in my tank and why N consumption is limited... maybe micronutrients toxicity...

One last issue althoguh way less important now -



> It's a matter of total N, not the form when it comes to plant health.


I believe it is important where the N is coming from. If it's from NH4 then it's in the available form and it's from NO3 then plants need to invest energy in transofrming this to the available NO3. I believe I learned this from Ms. Walstad.

Aviel.


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## plantbrain

> My private problem is that recently my NO3 uptake went down to 0.7 ppm per day and it used to be 2.5 ppm per day. I measure NO3 using lamotte high range and it shows N=4 that doesn't change after a week of 0.7 ppm per day dosing. I tend to relate this to the fact that in the last month I added ~50 new fish to my 200 gallons tank.


Well that might be.
You can do more water changes to see if it's from the fish though and alos keep tabs on the type and amount of fish food you add.

Just make sure to add more K+ inplace of KNO3(this still does not matter if you do large 50%+ w/c weekly)



> Yes and I believe I ruled those out - I checked, double checked and tripple cheked my CO2 (KH=4, PH=6.5), PO4 = constant 1.5 ppm where I add 0.35 ppm daily, I also add 2 ppm K (through K2SO4) daily and iron at 0.25 ppm daily half of it from CSM where I get the traces from, light is 2-2.5 wpg so really - I don't see any limitation and still N won't drop significantly. I think NH4 is generated and consumed immediately. Of course I can't measure it - one minute it's there and then it's gone -


Sounds reasonable enough. Your rates, 2.5ppm of NO3 vs 0.7ppm per day, how did you arrive at these? Daily=Weekly/7? How many weeks have you done this?
Weekly water changes?

One week etc is not enough to test your rates and get a good feel for them. There will be a range, not some absolute ppm etc always in any test.

Just remember that.
Test your rates in the best range of resolution for your test kits.
NO3 can be done weekly.



> I could never measure anything but 0 NH4 ever. But I thought that it's because tons of NH4 is generated and immediately being consumed by the plants. I thought that the N in the NH4 is now subtituting the missing 1.8 ppm (2.5 old NO3 minus 0.7 new NO3). Are you saying that total NH4 product is way below that?


Well, many simply do not have so many fish/feed as much/ have more light. At less light, you can supply 50% through fish waste w/o issue IME.
The N could be trapped in the plant biomass, bacteria, N2 gas removal, not 100% plant uptake, test kit errors, procedure/methods, number of runs etc.

This week it might be this rate for this set up. You need to have more averages, but now you have something to compare things to.
So that's good.

It's tough to assume that all the N is now coming from fish waste.



> If this is what you are saying then I have no idea what's going on in my tank and why N consumption is limited... maybe micronutrients toxicity...


I doubt this is occuring, those levels need to be quite high. 
You need to do more week runs and see if it makes sense.
Keep tabs on what you feed/dose to your fish.
Keep the CO2/PO4/Traces/K+/GH etc in good shape and then try higher amounts of NO3 and then see if the NO3 drops etc.
Try not feeding so much for a week etc.

Try several things/approaches, not just a quick jump to an assumption that it all must be coming from the fish waste.
You cannot test for that yet you seem sure that's it. Don't drive blind.
Scope out the other possible problems.

Quote: 
It's a matter of total N, not the form when it comes to plant health.



> I believe it is important where the N is coming from. If it's from NH4 then it's in the available form and it's from NO3 then plants need to invest energy in transofrming this to the available NO3. I believe I learned this from Ms. Walstad.
> 
> Aviel.


No, I have excellent growth rates using solely NO3.

*DW talks about energy, yet the largest limiting factor in plant growth is CO2, not NO3=> NH4 conversion* in her method and discussion. So this has much less effect and is much less significant I believe than she wants to argue.
N limitation is rather uncommon in macrophyte beds, but CO2 limitations occur in virtually all heavily planted systems.

If the plant is limited in 40%+ it's biomass for C vs 1.5% for N, which do you think is going to hve the greatest effect/impact on the plant?
And that is not even for limited N, that's just for the difference in forms(NO3 vs NH4). Some plants, but only some can use HCO3.
So this is even worst than than what I am suggesting.

The non CO2 issue really confounds the facts concerning what you gain from NH4 vs NO3.

In very controlled cases with some plants, we can show significant growth rate differnces one vs the other.

But in 99% of the CO2 enriched tanks, some NO3 is also needed in combination with wahtever ratio of NH4 is produced.

Therefore all of the references given are not applicable.
*They only compare solely one vs the other with specific plant species.
Not both in comination/ratios etc.*
The test also did not take into account algae, the cultures where sterile, something near impossible with most folk's tanks.

These are critical points in practical aquarium keeping and when making an arguement.

Also, that is for non CO2 tanks/systems.
Those test references did not test for CO2 enriched tanks.
Speculation is not fact. It might suggest, but does not prove a thing.
Adding CO2 also increases algae growth.

If you look into whether these references support a person's claims, then it becomes a completely other issue. Jus the ref's by themselves do not lend support.

I think folks have place way too much importance on NH4 vs NO3,
rather than supplying enough N. There is little, if any practical gain achieved by more NH4 s NO3.

I've done this in practical tanks, so have many others.
I've added more fish and also more NH4 inorganic.
I am not sure if DW has done this practical approach nor uses CO2.
She did not say so.

I test the stuff I speculate. I take my time and keep going back to things I am not sure about. So I tried testing NO3 exclusively, then add as much NH4 as you can w/o algae blooms(use a UV etc to keep the GW down) and try variations in lighting.

I know no one did this, I doubt many have done much with it since either.

I have not seen improved growth in any significant manner.
I have seen algae when we overload these systems from too much NH4.
I'd rather have more safety buffer and use NO3. I can add 20ppm of NO3, far more buffer than NH4 w/o algae issues also.

Concentration also drives uptake, the higher the concentration, the faster the uptake(it takes less energy).

Simply because there is some NH4 there, does not mean that the plants will remove it, it takes a certain amount/concentration to make it worthwhile, the plant also has a N demand it needs to fulfill. The nutrient status of the plants also is of question.

More fish is nice also, but stick with less light, the more fish/more light you have, the more stable the system will be(to a point).

This is starting to get into the N cycle and not the algae/plant thing. Start a new thread. You can read about it in TAG concerning N cycling.

Botton line, yes, you are getting more N from your fish wste, just don't get too much or let the other parameters get out of whack. But you run more risk in doing so, less becuase you have less lighting(slower uptake but less algae risk, better assimilation).

Regards, 
Tom Barr


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## Piscesgirl

This is a fantastic post  The only small thing that gives me some concern is the feeling I'm getting from this thread to starve one's fish and instead dose NO3. Of course, I'm sure that isn't the intent, and I supppose maybe I'm being a little over-sensitive to that point? 

How can we provide nice, fat, fish-bellies and still have algae-free tanks? (well, other than shrimp tanks - my shrimp tank I definitely overfeed and not a trace of algae anywhere *knocks on wood*)


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## aviel

I shall continue the N-uptake subthread here -

http://www.aquaticplantcentral.com/forum/viewtopic.php?p=20377#20377

Everybody are invited... :lol:

Aviel.


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## plantbrain

Well if you have a balanced fish load things ARE fine.
Try adding more and more fish.

I have never suggested starving anyone's fish.

Regards, 
Tom Barr


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## Piscesgirl

I see, your point was more about more fish (overstocking) as opposed to fish food affects per se. Sorry.


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## plantbrain

My point is not correcting, it's just showing that NH4 vs NO3 makes little difference as far plant growth is concerned, but NH4 will encourage algae growth and make the tank/system less resistant to algae.

*Or this can also go the other way, more resistant to algae if you FORGET to dose(fish will supply some N at least).*

Too low N will cause algae etc as well.

Regards, 
Tom Barr


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## Edward

plantbrain said:


> Concentration also drives uptake, the higher the concentration, the faster the uptake(it takes less energy).


Is there any evidence, research or testing done on this issue?

Thank you,
Edward


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## plantbrain

plantbrain wrote: 
Concentration also drives uptake, the higher the concentration, the faster the uptake(it takes less energy).



> Is there any evidence, research or testing done on this issue?
> 
> Thank you,
> Edward


More than you ever wanna know Edward

I taught Biology and enzyme kinetics for a majors course at UF.
I can show you lots of pain
I'll try to avoid that here.

The max reaction rate(V max) of an enzyme is determined by several factors. Temp, pH, and substrate concentration namely. I'll leave cofactors, inhibitors, feedbacks allosterics etc out of this for simplicity.

Basically:
The chance of an encounter with the Enzyme(E) + substrate(S) increases when you add more substrate with a set amount of Enzyme(E)complex.

Make sense?

This drives the enzyme to max levels of uptake(optimizes the efficacy of the plant's enzymatic uptake). At a certain point, the enzyme no longer takes up any more substrate once Vmax has been achieved.

Uptake is driven by enzymes, therefore concentration also determines uptake rates.

As temps increase, so does the reaction rate(uptake rate) up to a point till the heat denatures the enzyme due to destbalizing the weak Hydrogen bonds.

As pH goes outside the optimal range, the enzyme is destabilized and can denature the enzyme. This is due to the R groups on the amnio acids in the enzymes, thus altering the state of ionization of charged amino acids. Such as a COOH vs a COO-.

Each parameter has it's own shape vs reaction rates.

RR vs pH has a bell shaped curve
RR vs temp has a log shaped curve going up, then a sharp drop off at the denaturing point
RR vs Concentration starts off steep and then levels off slowly at Vmax.

Graphically:

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/EnzymeKinetics.html

More:
http://search.yahoo.com/search?p=Enzyme+kinetics&ei=UTF-8&fr=FP-tab-web-t-153&fl=0&x=wrt

Knock yer self out.

Okay, lots of biochem mumbo. Tom's all happy but what does this mean with weeds?

Well each weed/plant/algae has it's own max and V/2, these are different for different species.

So each has it's own fairly unique optimal substrate concentration, or say ppm level that the plant does best at and adding more will no longer help, Vmax has been achieved for that plant's uptake enzymes.

We do not know what the max level is for each obscure aquatic plant, that would take a lot of work/time.

So we find some that are tougher to grow, more touchy and use them as our canary/guinea pigs.

Then we add lots of light, lots of nutrients etc.
We raise these concentrations of substrates up and down till we get a response from the plants.

We can use these items to guess what a plant's Vmax might be for NH4, NO3, or PO4 etc......
And also assume that at an even higher substrate concentration that the lower Vmaxs for other species will also be driven at their maximum rates as well.

This is why adding more NO3 consistently is important. Keep the enzymes happy/running at high speed, the plant will be as well.

Regards, 
Tom Barr


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## plantbrain

An FYI, I discussed this issue relating to algae vs plants some years ago.

Algae need very little substrate concentrations to activate and optimize their enzymes.

So at low levels, they can take up more ppm than plants can, but at richer levels of nutrients, the plant outcompete them. This is true generally for smaller vs larger organisms.

There are other issues with this competition issue here(plants and algae are not in the same niche, but if you take this notion and assume it to be true), but the general theory is straightforword.

Too much worry about algae, not enough about plants.

Regards, 
Tom Barr


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