ID this in the sump please

[Hammer fish]

Please tell me what this is attached to the glass in my sump, also is it good or bad cheers

 

[mr_X]

I see Q-tip sponge. They are harmless. Nothing in the sump is bad BTW.

 

[MacDracor]

Mr_X is correct. They are also sometimes called pineapple sponge.

 

[Hammer fish]

How have I got so many just appeared in my sump should I leave them there or could I move them to the dt. Are they ok to keep

 

[MacDracor]

They're fine. Filter feeders. They are a silicated sponge.

 

[mr_X]

Leave them there. They are fine to keep.