Is this harmful?

[Soul]

Got some of these growing in my sump, about 3 already. Are they harmful? They are brown and have skirtings like zoos but have a stalk like anemones.

[PLataX]

bro, although the pic is not clear, but I think they r apitasias. They are generally considered as pest when kept near your other corals as they have a powerful sting. I only know of 1 coral which is more lethal than them and that is the elegance LPS. They can be rid off by injecting kalkwasser deep into their tissue or can be removed by tweezers, clipping them near the base (they should release their grip from the bottom if done correctly.

Else, u can keep them if u like them...hahaha...I once fed a neon tetra to it, gobbled it whole man!

[arcanehacker]

No they dun look like aiptasias. But they are some kind of anemone. Considered pests as they do sting corals and multiply fast.

I think I've seen LFS selling them on a rock.