Zoa's are closed.

[Treef]

I have this one group of Zoanthids that closed up suddenly after i did a water change 3 days ago. At first i thought that it closed because a bristle worm was crawling around at the base and irritating it, but today i took the group out of the water and the worm was gone , but the Zoa's are still closed. Only 1 polyp is opened and it seems to be a bit away from the rest. I noticed that sometimes the other polyps will open up partially then close again. My other groups of Zoa are doing good, opened and colorful. So anyone have any idea whats up with that one group? My water parameters are good 0 ammonia, 0 nitrite, less then 20 nitrate, salinity, and gravity are good as well. All my other corals are doing great, just that one group of Zoa's.

[aquarius77]

I would look for predators and get that nitrate to 0.

[parothead22]

I don't think your nitrates are the culprit as much as the possibility that your water flow and lighting may not be optimal. Many corals, sponges and Tridacna Clams require nitrates for them to feed on and grow. Without nitrates, they would possibly starve, or at best not grow in a timely manner. Now, a nitrate level of 20 may not be the best...as aquarius77 pointed out-I would shoot for 10 on the nitrates and focus on the water flow and lighting variables.
Another thing I like to do with continued success is to add iodine and perform a small, weekly water change!
Good luck!

[geoxman]

agreed with birdhead. What is the alk and PH? good luck