what is this

Could anyone tell me what this is growing in my feef? It looks like a sponge but not to sure.

 

i have the same thing i always thought it was a sponge i would like to know for sure too can anyone help out there

 

I thought it was a sponge also , I had brought some home from Boston when I was back home, I put a small amount in but it died

 

well hopefully it is a sponge and not some bad critter coocoon there are holes were something may come out but i hope not

 

Definitly a sponge.

 

Is it good to let them grow, I have one that is covering the entire back of a large rock.. but it also has spagettie looking things hanging off of it??? what is that?

 

Probably "budding" off to make more sponge. I would say let it grow. In the ocean sponge passes its volume oif water afew-many times an hour and filters out desirable foods for itself...alot may help water qaulity theoretically. But if it crashes it may hurt the tank.....ild say keep it at a decent size with a razor every now and then if you like it.

 

Thank Splender!