Closed coral

[aerialdronemaster]

hi
All my corals are doing good , but this guy recently is closed , it used to be super big.
What could cause it?
All water parameters are ok. Just phosphate went up to 0.6 and alkalinity 6.9. , I will replace some water today

 

[Ron Reefman]

Corals and anemones have minds of their own. Many things can cause them to close up short term or even long term. Don't rush to make changes. I've had lps corals stay closed for weeks and then open up again. Maybe it doesn't like the flow it's getting?