Zoas died...dunno why...

[atrialfib22]

Ok...so as the title says some of my zoas seemed to have died and I am not sure what's really going on.
All of my corals are fine and open except this small isolated rock that I've had in my tank for about 4 weeks. It had a frag of about 7 polyps...and now they are all shriveled up and pretty much gone. Along with that there now is a yellow "thing" attached to the small rock. It looks like a stretched out piece of gum...and I only noticed it like 4-5 days ago...
At the time I didn't think anything of it...the polyps were still there and I thought they were closed because they might have gotten picked on by my clowns or my cleaner shrimp (whenever they touch it, of course the polyps close...so I thought that's what was going on)...but today I get home from work and the polyps seem like they are gone!
I can't seem to take a clear picture of the yellow thing with my camera right now...does anyone have any idea what that yellow thing could be and if it could be the culprit? (some sort of nudibranch maybe? or parasite?)

Any help is much appreciated...
Here's some more info about my tank
20g (high) - reef...
22 lbs of LR, 20 lbs of LS
pH = 8.2
Temp = 78.9
Spec Grav = 1.024
Ammonia = 0
Nitrites = 0
Nitrates = 20
dKH = 11
Calcium = 320
Phosphates = 0
2 False Clowns
1 Red Firefish
Cleaner Shrimp
Peppermint Shrimp
Torch Coral
Duncan
Candycanes
Blastomussa
GSP
Clove Polyps
Assorted Zoas

 

[atrialfib22]

Ok so last night after my lights went off and the moonlights came on I noticed the yellow thing started to shrink...so I am assuming it uses light as part of feeding. Any clue anyone?

 

[debbie]

zoas are pretty hardy so you need to find out what is in there that is eating them. This yellow thing, can you take a picture of it??
Also, is there any of your other corals touching these zoas??
Don't toss them out just yet, I had some neon greens that did not open for 5 weeks after my lfs glued them for me. She handles them quite rough and I think got some glue on the tops of them. They are now open and good.
Is there any of the polyp left at all?? Are these the only zoas in the tank??or
I see you have a peppermint shrimp, this is just my opinion, they are not great for corals. I had one once and watched it pick away at my mushrooms
till there was nothing left, this might be your culprit but you would have to watch and see for sure.

 

[nemo_66]

i agree. it could have been your shrimp or a parasite. thats about all i can give you. sorry if that didnt help.

 

[tizzo]

You can also look for sundial snails.
Heck to treat against any possible bad hitchhiker, just do the freshwater dip. That will eliminate any possible zoa eater.