I bought a tank that contained this live rock, tank had been set up around 4 years. Can anyone tell me what is on the rock? It opens in the daytime and will move around.
doesn't appear to be a nudibranch, I think its the picture angle,making them appear that way. They attach and stay in place when they find a spot they like. Sorta look like a pink or brown polyp with a white body. Look at the one in bottom left first picture he's attached.
its a nem for sure,i have one they are very small like less then 1/4" mine moves too if i move the rock,pretty sure its a mojano nem,i havent killed mine yet its in my 10 gal tank,ive even light deprived it with 2700k lights and still it lives
Okay ya'll this tank was up and running for around 4 years. We purchased it last week, moved it and set back up the same day. All rock was kept under water. Whatever these critters are had been in place long enough that Coralline algae had formed around them, there are marks in it where they were attached. I think the move is what is making them move around, either from a mini cycle or just not liking the location of their rock.They sit down flat like mushrooms but when they move they have a fat white body that actually crawls. Their size is about the same as the end of a pencil eraser some bigger some smaller. No they are not multiplying that I can tell.