Found in sump

[MapleLeafReefer]

I found this stuff on some live rock in my sump. I was removing the rock in favor of bio brick. Any idea what this is?

 

[MaxTremors]

Its a sponge. And some feather dusters/fan worms.

 

[MapleLeafReefer]

Its a sponge. And some feather dusters/fan worms.

Is a sponge a good thing to have, a bad thing to have or an indifferent thing to have?

 

[jeffchapok]

They are filter feeders so I consider them beneficial.