Brown mushroom like coral?

[angela1]

This was given to me by an experienced hobbyist who didn't speak English. Can anyone tell me what it is?

http://reefcentral.com/gallery/data/514/219833brown_mushroom_like_coral.jpg

 

[KarlBob]

They look like palythoa to me. They're often called palys (prounounced "pallies"). Depending on the difference between your lights and the former owner's lights, they may change color as they adapt to your tank. Some palys can spread rapidly, and take over adjacent rocks, so you might want to keep them isolated on their own rock.