I was just about to do some tank maintenance and was looking the corals over from my exercise ball in front of the tank (It makes a nice low seat!) and noticed something all over the underside of one of my pocillipora (I think). It's yellow ... could it be a sponge trying to take over? Fungus? Next, when I lifted it up I noticed some little tentacles still on the rock and got to looking closer. It almost looks like tiny mushrooms but the tenticals are really long, almost like a frog spawn or hammer or something. There are little tips on the tentacles that are light. There seems to be a mouth of sorts in the center and the tentacles seem to be more in a circular pattern rather than all over like frogspawn or hammer. I've found about 5 so far and I'm sure there could be more. They also close up with touch. The pics aren't great but I took a video that shows them much better.
So after googling "baby anemone" I found some pics that look identical. Seems it may be a pseudycorynactis or corallimorph.. still can't find a difinitive if they are desireable or not! Anyone have any experience in this dept? Still don't know what the yellow thing is though.
The yellow thing looks like a sponge to me and yes that is a "Ball Anemone". Some will tell you a Strawberry Anemone, it looks similar but is not a Strawberry, they are cool water species.
What are your thoughts on being a nuisance or harmful nem? If they will spread like aiptasia then I want to get rid of them but if they are fairly peaceful or small I don't mind leaving them. They are pretty! These are currently very tiny, like dime sized at the most when extended. And I guess that is just that big one first in the video. They rest are smaller. Also, do you think that sponge is smothering the picollopora or do you think it just grew on dead area? Should I remove it or leave it?
I have never had a problem with them. I leave them alone. Most of them will set up shop u der an overhang or in a shadow somewhere. Shine a light in your tank in the middle of the night and you will see more of them. As for the sponge, it is probably on dead tissue. I wouldn't worry about it.