Is this aiptasia?

[Jwj]

My tank is new. Only about 4 months old. These came with a live rock and have been spreading. They seem to grow on the underside of rocks or spots that don't get much light. They don't seem to have the long tentacles I see in pictures of aiptasia, so I'm not sure what they are. Any thoughts for ID and whether I need to get rid of them are appreciated.

 

[Spare time]

Those are harmless pineapple sponges aka what spongebob lives in . Super common.

 

[vetteguy53081]

They are short lived and derive from silicates likely from an RO unit and mainly found in shaded areas of tank and sump
Soon they dissipate and are gone

 

[Jwj]

Great! Thanks both, for the reply!!

 

[shanescycling]

Thanks for asking this question! wish I would have seen this 2 hours ago before pulled out a rock I had with them and picked them off.