Colt Coral doing not great, found a weird thing underneath it.

[Rijos Reef]

Hello,

I have a colt coral that is not doing great. It was closed for a week. And now it opens up now and then and the polyps are not as full as they used to be.
I found this thing underneath its foot. It has two gaping holes as far as I can see and sometimes they close. My questions:

What is it?
Could this be the source of the colt's problems or is he just an unhappy colt? (other corals seem just fine)

Thanks for helping out!

 

[elysics]

That's a tunicate, but i doubt it's the reason the coral is unhappy, did the coral maybe just shed it's skin? Since it opened again without you changing anything

 

[Rijos Reef]

Thanks for the clarification. Well I don’t know. It was closed for a week and from what I have read on the forums shedding could have been the reason for that. But it has been weeks now and he doesn’t seem happy in his new skin. So the question now is, can a tunicate irritate a coral in a way? And if not could there be another reason? Thanks again!

 

[elysics]

If in doubt you can always remove it and see, would be a shame about the tunicate though.

If I were in your place I'd look for other causes or cut off the colt to save both animals. But I'm a bit biased towards tunicates so take that for what it's worth

 

[moz71]

Not sure about what exactly is in picture but when I first glance at it it reminded me of my first colt coral. I had a colt coral for over a year doing great then it started acting very unhappy and slowly started degrading. One night I thought I saw a small slug on it so in day time I took it out of tank and under the rock it was growing on where 3 HUGE whitish nudibranches. I quickly discovered they were coming out at night to feast on it. I am not saying that Is what is in pic or your issue but something might want to check or be aware of