Appears on a piece of rock which does not get a lot of light(In cave). Light brown, tips have little bubbles on end of tips, kind of translucent. Sorry for the bad pic, just couldn't get a good pic.
Looks like I found two more, one in an old abandoned shell (see Photo) and another one located on the bottom of a rock. If it's a ball anemone, how do you get rid of them. In addition I found half of an emerald crab in the bottom of the tank. The body from the crab was not from molting.
The ball anenomies are fine. Even though the have nemosyst (spelling?) they are in the mushroom family according to some.
When you you said you had some half eaten crabs and the next picture showed what was clearly a whelk I couldn't stop laughing :lol: Sorry.
I would leave the anenomies but isolate or remove the whelk.