What makes zoas shrink?

I got several frags of zoas a few weeks ago,all are doing great,sprouting new polyps,fully open and generally looking good........except one,it's a small frag with like 5 polyps,but I swear,everytime i walk past they are even smaller yet,they are wide open and look fine,just shrinking.I've checked my water and all is good
Sg-1.025
ph-8.0
alk-9
nitrates are at 10
cal-420
mg-1300
0- am or nitrites

These zoas are in the same location as several other zoas,so i'm pretty sure i've eliminated flow or lighting.All other corals in the tank are doing fine,couple acros with good color and PE,a few lps,all look good and a few shrooms(no where close to the zoas)that is all the coral in the tank.The polyps of the zoas in question are about 1/4 of the size of a nomal zoa and shrinking fast.No signs of pest or nudis either.



Any ideas as to why they would be doing this??

 

I don't know, but it seems to me that they just do that sometimes. Lighting may be an issue. They may be getting more than they want, they don't open as much or become smaller if they are getting more light than they want.

 

agreed, sometimes I think they just do that. My yellow polyps were doing that for a while. They were down to almost nothing and I was about to toss the plug for fear of spreading something. I decided to wait until tank maintenance day just to limit hands in the tank time. Well that day they started looking better, and now not only are they better but i probably have double the heads and they are bigger than they ever were.

Give em some time.

 

The lights sound like a good culprit as they are very dark blue zoas and they have lost a little color (some,not much) as well.I'll try moving them to some shade and see if they improve.Other wise i'm pretty stumped.Thanks for the hand 2in10.

 

I've also heard of this happening for no apperent reason,but I just don't like it when it happens to mine .
Thanks khowst,I just don't want to loose these ones because they're pretty cool blueberry limeaides,heres a pic of when i ordered them

 

Zooanthids and palys, do not all come from the same zone habitat wise, and geographically( yes I just stated the obvious). Point is that it might do better in different area of tank under different lighting.. They sure are pretty though grinder.

 

The zoas and palys in my tank that were sort of (hopefully) the last thing that I have had issues with that I couldn't figure out. I have not had major problems with them, but some have not grown much, and every now and then a head would slowly shrink until it was gone. There were a number of them that were just hanging in there. For the amount of time that I've had them, they should be everywhere.

I looked for pest very carefully, moved them around changed flow, nothing really helped until I did a Furan 2 dip. I dipped all of the zoos and palys that I have, and after only one dip there was a remarkable recovery. Three dips are recommended, and I'll probably do one more for a few that could still be doing better. Within a week of the dip, there were new heads growing from zoos that had held the same numbers for months.

I got the information from here Furan 2 dip The third and fourth picture down looked just like a few of the small colonies that I had.