Is this some kind of sponge?

[Reefo25]

Just noticed a few of these guys growing in my sump

 

[Thespammailaccount]

Just noticed a few of these guys growing in my sump

Flatworms perhaps hard to tell from the photo

 

[Acan_Fan]

Pineapple Sponge. Good guy! They will come and go depending on how much you feed.

 

[WV Reefer]

^ yep. Pineapple sponge.

 

[jaiken1120]

Pineapple sponge. Usually see alot first few months after a tank is fully mature and over time dwindles down to few .

 

[Reefo25]

Ok thanks everyone