some pretty clear studies that higher phosphate will limit calcification and lower levels will promote it (leading to burnt tips as calcification outpaces tissue in low P acropora tanks with abundance of carbonate, calcium and magnesium).
This is old science and (mostly now) a hobby myth – both the proposed mechanisms and the supposed cause(s).
I have several journal articles on it....all calling out something to the effect: "maybe science was mostly wrong about P being bad....and nutrients in general too."
Nutrients appear to be good EXCEPT under a sort of narrow range of circumstances. And that narrow range of circumstances really aren't mysterious after reading either.
Check out "microbialization" in relation to algae and coral reefs...IMO burnt tips is from this.
...for example: Global microbialization of coral reefs
...and this: Role of elevated organic carbon levels and microbial activity in coral mortality
...and this: Role of elevated organic carbon levels and microbial activity in coral mortality
Also this:
If you browse around the Coral or Nutrients tags on my blog you can find quite a few more...all singing approximately the same song.
Carbon limitation seems to anchor the reef ecosystem...nutrient levels seem mostly secondary, but they are nutrients not toxins....they don't hurt anything. They do seem to raise the potential for bleaching if there's a rapid change in conditions, however.
Rising carbon levels on the other hand....