Help me identify this filter feeder(?)

[Ice]

These guys randomly showed up as one or two and now I have a handful in lower light and shaded areas

 

[DSC reef]

Looks like tunicates, harmless

 

[ISpeakForTheSeas]

+1 for colonial tunicates; technically harmless filter-feeders - that said, some species can be invasive to the point of growing over corals and smothering them, so I typically recommend isolating them somewhere you can easily control their spread in the tank.