Zoanthids water flow causing them to close ocasionally


Premium Member
I have a rock with a couple different zoanthids and palys, I have noticed that occasionally all the zoanthids will move because they are hit by some random flow, when this happens there is a colony in particular that almost fully closes, and then re-opens within a few minutes. Another colony is barely affected, and the rest don't seem to mind, specially the people eater palys seem to just stay open at all times. I have them placed about mid level on my aquarium, and I have the tunze in pulse mode 45% main and 25% pulse on 8 seconds interval, and a koralia 1150 gph, plus the return pump of course, I do not think my flow is excessive at all. I figured in nature zoas also get random flows that close them ocasionally, so I was wondering if this is something that zoanthids like i.e. being ocasionaly hit with a random flow that closes them, or if I should move them to an area of less flow?

Also it seems a colony is bleaching slowly, they are all open, they are mostly purple with a whiteish dot and green skirt, and starting to become a lighter shade of purple starting from the center, afaik they weren't like t his when I got them 8 days ago, but I could be wrong... I only have a marine Orbit LED 48-60 which outputs 46 watts, running at 85% actinic and 39% whites, and I have them positioned about mid tank, certainly that cannot be too much light?. Or are there other things that could cause them to bleach?, water quality looks good, and all my zoanthids are fully open and extended, well with the exception of 2 polyps out of about 70-80 from different colonies. None of the other colonies in the same rock are bleaching, I have 5 different zoanthids/palys in this rock sized about 5 inches. Should I move them lower?. I have a frag of green candy cane coral at the same height, which seems to be doing great.

Water is testing at 0 ammonia, 0 nitrites, 0 nitrates, PH 8.3, SG 1.023, PO4 7 ppb (about .02) with ultra low hanna checker, temp 77 F I use Kent marine salt, I don't have a tester for calcium or Alkalinity, but I do weekly water changes which should keep them stable, getting some checkers for those soon. Tank is about 7 months old, no real algae issues. Dipped rock in coral rx when I got them 8 days ago, and dipped again a week later (yesterday) just in case, nothing really came out in either dip.