Low Phos= Low Alk?

[coralboi56]

Howdy,

So I've recently won my battle of high phosphate (went from .9 to .02), but i noticed my alkalinity took a nose dive over the course of the battle from 11.4 to 6.7. I've heard from a coral farmer that that should happen, but my question is why does this happen?

 

[Randy Holmes-Farley]

it does not always happen, but it may be (and has been shown to be true in some cases) that some corals and/or coralline algae may grow faster in lower phosphate conditions, increasing the demand for alkalinity.