Help Id

[robreefer420]

I recently set up a 20gallon tank and got some aquacultured rock from the Caribbean. Today I noticed some black things on the rock I can't ID. Any ideas?

 

[ISpeakForTheSeas]

Looks like colonial tunicates - harmless filter feeders, but some species can spread pretty invasively. You should be able to manually remove any you want gone pretty easily, though, so I'd personally keep them and just remove some as needed (if necessary) to make room for other stuff if it turns out to be one of the invasive ones.