Lowering phosphates by dosing nitrates?

[WillB]

Is this something that is done or should be considered? I’m thinking if your phosphates are slightly above what you want them as and you have low nitrates you should dose nitrates as that would be the limiting factor in phosphate uptake? I know it isn’t a 1 for 1 ratio and that there are many more factors but I’m curious about it.

 

[Randy Holmes-Farley Verified Community Expert]

Is this something that is done or should be considered? I’m thinking if your phosphates are slightly above what you want them as and you have low nitrates you should dose nitrates as that would be the limiting factor in phosphate uptake? I know it isn’t a 1 for 1 ratio and that there are many more factors but I’m curious about it.

This will only work if nitrate is low enough that it is limiting the growth of some organism, such as macroalgae. It needs to be pretty low for that (probably less than 1-2 ppm), and even ammonia may be adequate for many organisms as a source of N, since many algae prefer it over nitrate.