They are the parazoanthus genus that is related to the other zoanthids. They are not poisonous like palys so polyp munchers are more likely to snack on them. My toby has decimated my yellow polyps. They keep trying to come back though. I guess I should move the rock to my refugium for a while.
The are photosynthetic, and will eat whatever floats by. I have even seen one eat a piece of pellet fish food. You don't have to worry about them eating your fish or stinging other inverts though.