Hydroid/Sponge? On coral

[draxus]

So something is choking out my Zoa (first pic). My winter pipe organ has some cylinders as well. I was looking around all of my other corals, not sure if it’s on the Duncan or the Xenia that’s just “roots”

I only see it in coral
Plugs (which were dipped in coral rx when I got them). So if the answer is remove affected coral that is an option

 

[ISpeakForTheSeas]

Those are sponges.

This one is a pineapple sponge, so you can rest assured that it's harmless.

These corals don't seem to be bothered by the sponges, so most likely not a problem here (although the coral in the first pic quoted above seems to have some algae growth on it, so something is bothering that one, it's just not the sponge).

This one concerns me - if the coral was in good health in your tank for a while, then suddenly went downhill with the appearance of the sponge, that would be a good indication to remove the sponge. If you only had the coral for a little while before this happened, then it's possible the sponge is still harmless - but either way, it looks like it may well turn invasive.

So, this one may be best to remove just to be safe - the others are most likely harmless and shouldn't give you any trouble.