Yeah that’s the other problem can’t figure that out, phosphates are never above .1 most times .05-.08, I don’t over feed, as a matter of fact I forget to feed sometimes, my lights aren’t on too long, my blues run 8 hours, whites only 2.
Don't misunderstand nutrients. 0.08 ppm phosphate is likely more than enough for any algae, and 0.8 ppm will not likely make it grow any faster.
Trying to limit algae by reducing dissolved nutrients is a very hard game, since one risks starving corals unelss you feed the corals particulates.
This published article tested a lot of species of macroalgae for what is limiting it.
The base case of unenriched seawater was 0.12 uM phosphate, or 0.011 ppm.
The base case of ammonia was 0.007 ppm and nitrate + nitrite 0.02 ppm.
Raising phosphate from 0.01 to 0.2 ppm only made one of them grow faster (codium) and it was only a little faster.
OTOH, boosting the ammonium from 0.007 to 0.9 ppm boosted all of them except the codium.
Significantly, adding both ammonium and phosphate together only made a few of them better than the N boost alone.
This is an example of the concept of a limiting nutrient. One level of something limits growth, and everything else just gets taken up as needed, no matter how much is there.
