You start off by stating this: "Even if the test reads 0 ppm it is still there, and plenty for plants. Don't worry." and later state this: "No P or N would cause no algae but also no plants". I understand the part about the lack of sensitivity for the liquid based test when level is that low, but it's the "plenty for plants" and "no plants" part I don't understand. Please explain.
What makes my results with GSA interesting? It's definitely not unique. Other members on this forum with planted tanks will tell you the same thing: GSA present, increased the PO4, GSA went away. However, lighting plays an important role in this. I have a planted shrimp tank and I do not dose phosphate. It comes in naturally through their food. But I don't have outbreaks of GSA or other algae because the lighting is at the low end of medium.
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When I say "Even if the test reads 0ppm there is still plenty there" I mean that there is a level there that the test cannot detect but still enough for plants. I assume there is still N there as well. When I say "No N and No P means no algae or plants" I mean actually none. Actually 0ppm. I experimented with carbon dosing and GFO to get a ULN fish only system in the past. I say that the results are interesting because conventional logic promoted by people such as Julian Sprung in his book on Algae promotes the idea of phosphate removal for green hair algae. I often promote that myself because most aquarists are completely ignorant of phosphate and usually have very high levels. However, there are also many people now saying that maintaining a proper N to P ratio in a planted tank gets the same result. In your case, you added some P to restore the ratio. I find that interesting. Also...In a planted tank there is another player which is studied very little called Aleopathy. Basically chemical warfare done by the plants. Sometimes against Algae. Because I never let my phosphate stay to high, I never get most of the green algae but I have a nice ULR Hanna Phosphate checker now and I hope to be able to collect samples of various algae infested systems and try to figure out the conditions that make specific algae thrive someday
Thanks for all your input
Update: I found this
http://buddendo.home.xs4all.nl/aquarium/redfield_eng.htm
It supports your method will work.
Also, A very well regarded Aquarist and Chemist named Randy Holmes Farley says
"I agree. Cyanobacteria can get nutrients in ways that green algae cannot. Specifically, cyano can fix nitrogen from the air, so doesn't necessarily require ammonia/nitrite/nitrate the way green algae does.
Cyanobacteria can also take up and metabolize organics more easily than green algae, and so can thrive in organic rich waters that have little impact on green algae. "
It is regarding salt water but the principle is the same.
Link is here :
http://www.reefcentral.com/forums/showthread.php?t=1340469
Which supports phosphate is a better way to control algae then nitrate, although both can be used with the green types of algae. In your case if you had lowered N instead of raising P you would have most likely got the same result. I should mention that any N or P in the water column is just extra that the plants did not take up. At least not yet
Rates of going in and coming out play a role. I prefer a well lit tank so I choose not to use low light as a weapon.
