What's this thing on my rock?

There's this green thing growing on one of the rocks I just bought at the LFS and I have no idea what it is. I put the rock down in the sump for now until I could figure out what it is. Anybody have any ideas?

 

Sponge, awsome to have, helps keep the water clear

 

Oh cool! ;D

 

Just make sure it doesnt take over, sometimes i trim mine back, and i just toss it in the sump but make sure it doesnt hit the air

 

Can I take it out long enough to pull it out of the sump and put it in the main tank?

 

I would not, just put a bag in the tag and put it in the bag under the water and do the same to put it in the sump

 

I have those in my overflow they are really cool.

 

Picture is too fuzzy for me to offer an ID but if it is a sponge...

No. Sponges must be under water not just wet. Air will get trapped in the sponge and it will die if it is taken out of the water.

 

i have two sponges there cool and you dont reeally have to take care of them

 

Didnt know it would be sponge, do they come in yellow?
If so then I have a yellow sponge in my tank