Zoas not opening

[bwiniecki]

i got about ten zoa frags from my LFS about a week ago and 8 of then fully opened up in about a day or two. The other two are completely closed and i'm starting to get concerned. Is this normal?

 

[rkpetersen]

It's not unusual. There's something they don't like. Many possibilities.
Could be too much light. Could be too much or too little flow.
Could be something missing from the water, like iodine.
Could be toxins in the water, as from dinos.
You're right to be concerned; if it persists, the polyps will eventually shrink and melt away.

 

[joshinjosh]

agreed, also check your alkalinity. zoas a pretty sensitive to alk swings