FAQ: If Seachem PhosGuard™ doesn’t release aluminum that will stress corals, then why did my corals close a day after I added PhosGuard™?

Phosphate plays a major role in the chemistry of the aquarium, and an overdose of PhosGuard™ is capable of very rapidly lowering the phosphate concentration in the aquarium. If an overdose of PhosGuard™ is used, it is possibly to lower the phosphate concentration so quickly that corals become stressed.