Originally Posted by mattycakesclark
Water companies might add a orthophosphate feed (basically a chain of phosphate I believe).
Orthophosphate is more commonly known as phosphoric acid. Some reef tank folk say that algae has a particular love for phosphates in that specific form.
I would have to agree, because I have induced some crazy algae blooms using "pH Down", in the old days when it contained phosphoric acid. Later they put a warning on it not to use it in planted tanks because of that. And eventually they switched to sulfuric acid instead.
I have also seen people with high phosphate levels out of the tap, who have solved their algae problems by switching to RO water, or using a phosphate absorbing resin.
But you can add all the potassium phosphate fertilizer you want, and not cause algae.
My API test does register phosphate in my tapwater at about 1ppm. It's only for real in-tank readings that it goes nuts.
That amount is not enough to cause any noticeable algae problems for me. Nor has it allowed me to decrease my phosphate dosing. If algae can have a preference for phosphoric acid, then maybe plants have different preferences too; which would work out nicely for us.
I would love to see someone besides myself try replacing the potassium phosphate in EI with an equivalent amount of phosphoric acid and potassium sulfate, and report the results on both plants and algae.