# Excess nutrients do not cause algae



## IUnknown (Feb 24, 2004)

The idea that I've always struggled to understand is that excess nutrients do not cause algae. Maybe I can work on a flash animation that would explain my confusion and help others understand. I was thinking of bar graph's on the left of the animation showing concentrations of micros and macros, and then bar graph's on the right showing algae and aquatic plants growth rates. We would start with a balanced tank, where the nutrient concentration favors the growth of aquatic plants rather than algae. Then overdose with say Iron. Plant growth/momentum would increase and some other nutrient would run out. When that nutrient ran out, the plant growth would stall and algae would start to grow. Do I understand this concept correctly? Is this how it works if you overdose any of the Macros or Micros?


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## Phil Edwards (Jan 22, 2004)

I've always understood the "excess nutrients do not cause algae" statement to either mean:

a: short term excesses aren't a problem. ie, dosing high amounts of Nitrate (20+ ppm) because the plants are going to remove it from the water column in a short period.

corallary: As long as nutrients are in balance *and the plants are growing* then excess levels aren't much of an issue (in the short term)

b: One can add an excess of one nutrient because that tank uses X nutrient more than others.


My response to that is: Prolonged excesses of all or some nutrients will contribute to algae. If there are levels of nutrients higher than the macrophyte population is able to absorb/utilize then algae will pick up the slack.


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## plantbrain (Jan 23, 2004)

I do not see it that way both observationally nor theoretically.

I've run a 20 gal with loads of light(5.5w/gal pc), good CO2(30ppm), no fish/herbivores(and did it with them as well), and dosed 20-30ppm of NO3, PO4 to 2ppm for long extended peroids(4 months).
I dose traces way beyond the needs of the plants.

I had the best growth I've seen.
No algae, no herbivores either.

That's virtually all plant power, not other things influencing the algae.
That is also a long enough time peroid to have significant algae and opportunity for algae to bloom. 

The tank was pruned and tended, filter cleaned etc, but nothing special.

Algae need a reason to grow. They also are much smaller and as such require far less nutrients concentrations to sustain high growth rates than the much larger plants.

There is a graph in my first article that explains this visually. Alage(microphytes) are not in the same niche as plants(macrophytes).

That assumoption that they are will get you into trouble.

This is also observed in natural lakes in FL, you add PO4 or NO3, you get more plant growth, niot algae growth if the lake is already dominated by plants, this is not the least bit surprising to aquatic weed researchers.

You also do not find good macro algae growth in nutrient poor regions, you do fine very small plankton. This same concept is true in SW systems as well.

Regards, 
Tom Barr


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## Peter(09) (Jan 18, 2005)

I certainly do not think I am an expert on planted tanks (well may be in growing algae ...... no wont go that way) but I have read a lot of articles on growing algae, I mean plants, and there seem to be lots of different experts who produce great tanks but do it differently!

Tom, in his previous article indicates that excess nutrients are unimportant, while others suggest balencing Nitrates and Phosphates, while other suggest limiting certain nutrients etc.

I have come to the (uneducated) conclusion that once you have a tank which is going well and the plants are being driven hard then you can throw most things into it and it will take it all. On the other hand if you have a tank that has not taken off yet and you do the same ....... have a green and slimy day.... Recognising the difference is the first step to having a good planted tank.

Finally, I suspect that what ever it is that actually stops algae growing is as yet not fully recognised, there is something associated with plant growth that stops algae growth, but thats just a gut feeling.

[Soap Box mode] = off

:-#


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## defdac (May 10, 2004)

Peter(09) said:


> Finally, I suspect that what ever it is that actually stops algae growing is as yet not fully recognised, there is something associated with plant growth that stops algae growth, but thats just a gut feeling.


.. and good plant growth can only be achieved with non-limiting levels of everything - and because plants become limited long before algae, the nutrient-limiting-aproach is a dead end for planted tanks.



> If there are levels of nutrients higher than the macrophyte population is able to absorb/utilize then algae will pick up the slack.


Plants need continous high levels of nutrients to grow well. If one nutrient limit the growth of plants ammonium rise and trigger resting algae spores.

Limiting = Algae. Stable high nutrient levels = Resting algae spores and phenomenal plant growth.


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## Peter(09) (Jan 18, 2005)

I do not disagree with what you say, the problem is that commiting to adding high levels of nutrients to a tank is rather like jumping out of an aeroplane, everythings go to be right otherwise you in for a fall :shock: 

Many beginners have most probably started this way not realising that there is something else thats going to limit plant growth in their tank such as the CO2 levels or lighting, or plant types or..... and end up with a solid green block.

The other thing to try and understand is that some people do seem to have success by limiting nutrients ..... how do we explain this?


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## defdac (May 10, 2004)

Peter(09) said:


> I do not disagree with what you say, the problem is that commiting to adding high levels of nutrients to a tank is rather like jumping out of an aeroplane, everythings go to be right otherwise you in for a fall :shock:


Only the CO2, the hard part.



> Many beginners have most probably started this way not realising that there is something else thats going to limit plant growth in their tank such as the CO2 levels or lighting, or plant types or.....


Only the CO2-level. The light is the one thing a beginner would want to limit. High CO2 and nutrient levels, less light = More wiggle room.



> The other thing to try and understand is that some people do seem to have success by limiting nutrients ..... how do we explain this?


That is voodoo if it works. Limiting something to grow better. That does not compute.

But some folks (with voodoo-hands) manage to micro-manage and balance out the nutrients exactly to the low carbon supply and high light. But man, that's roulette. It can work for some with green fingers and an extreme amount of feeling, but I wouldn't suggest doing it to beginners.

Dump everything in (KNO3, KH2PO4, Micros), crank up the CO2, go easy with the light and watch everything grow like crazy. That's a tip for beginners.

Not the voodoo-stuff.


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## plantbrain (Jan 23, 2004)

Peter, as far a new person, I do not suggest they use high light. Nor CO2 even............it depends on the goals...........

Low light+ CO2 is generally a good mix of good growth and ease of care and gardening, non CO2 tanks are not the best for gardening aspects.

"I certainly do not think I am an expert on planted tanks (well may be in growing algae ...... no wont go that way) but I have read a lot of articles on growing algae, I mean plants, and there seem to be lots of different experts who produce great tanks but do it differently!"

No, they don't actually.
In each and every case they address the plant's needs for a give level of light and growth rate. The rate might change, but not the focus.
With a non CO2 lower light tank, fish waste alone can supply most of the needs of the plants.

If you increase the demands of the nutrients by adding more light=> this increases the CO2 demand, adding that increases the nutrient demand and that increases the growth rate.

You can add nutrients a number of ways but the inputs always balance with the outputs. 

The rates of growth might change or be different, but not what goes in/out. 

This also applies ot reef and macro algae marine systems, non CO2 and CO2 enriched tanks.

This is a myth that each method is "radically different", rather than are much closer than anyone has ever suggested beside myself.

This might bother some people, but that's normal for me
But I see much more similar observations and methods and when I test this notion, I find I am able to predict things accurately. 
This also occurs at the lake/pond level. It is not just planted tanks with CO2.

"Tom, in his previous article indicates that excess nutrients are unimportant, while others suggest balencing Nitrates and Phosphates, while other suggest limiting certain nutrients etc."

They are wrong. If they were right, where is my algae? Where is my poor plant growth? Have they actually tried it and tested in a controlled manner?

Answer: no. If they had, they overlooked something and did not explore both sides of the coin, so that's their bad. If you do not try to achieve more than you have already mastered, you will not grow. 
Some might prefer a lean plant look............these are generally folks with a lot of experience, that have grown into this hobby with a set of thoughts that believe excess is bad. 

You can walk close to this edge and get burnt or simply not worry about it. 
Many still will lower the nutrients down for a temporary showing, then later raise them back up. This works with some species for red color.

"I have come to the (uneducated) conclusion that once you have a tank which is going well and the plants are being driven hard then you can throw most things into it and it will take it all."

Yep.
Lakes, ponds as well.

" On the other hand if you have a tank that has not taken off yet and you do the same ....... have a green and slimy day.... Recognising the difference is the first step to having a good planted tank."

Seeing why a tank did not take off is more important. Where there enough plants? Good CO2 etc?

There are very explainable reasons for failures.
Many folks have done plenty of that

Experience is good to learn from, as long as it's not your own.

"Finally, I suspect that what ever it is that actually stops algae growing is as yet not fully recognised, there is something associated with plant growth that stops algae growth, but thats just a gut feeling."

NH4 competition, plants are already large sized "adults", algal spores are like tiny babies, they gain much more from NH4 than NO3, therefore they do not bloom unless there's enough NH4 present.

Don't believe it? Add some NH4 to your tank and see. 
Next try the sasme thing ona tank packed with plants also and add NO3, then keep adding it till you hit 30-50ppm.

Then you'll see the NH4/NO3 issue.

You can add carbon to remove any alleopathic chemicals that might supress algae, you still have the supression(actually even better since the carbon removes NH4, you guessed it!)

Regards, 
Tom Barr


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