fast growing coral: friend or nuisance?

[Dan J]

Hi all. I've posted a pic of a volunteer coral(?) colony growing in my tank. The rocks came from Tampa Bay Saltwater and continue to reveal fun new life forms. These guys seem hardy and are growing quickly. They started on the bottom of the rock and were all white. I flipped the rock over to get them direct light and they have darkened and nearly doubled in size in 3 weeks. They seem harmless, but I'm a little worried about their rate of growth. Could this be something i should worry about taking over my tank? Thanks for any answers/thoughts. I always enjoy the responses I get on here.

Dan

 

[Chris86]

I can't tell for sure, but it seems to be some sort of zoanthid or paly. Generally, people try to isolate them to their own rock so they don't spread all over the tank. Be careful when handling those. They may be quite poisonous.

 

[Highgrade]

Looks like a sea mat-paly which also I've heard them called sea mat anemones also. Fast growing from what I understand.