Help identify this?

[Rich82]

New to salt water tanks and found this while cleaning my tank. Please help identify! Looking at the mushy, yellowish colored item, right hand side.

[eli@fijireefrock.com]

Sponge
filter feeder good

[Rich82]

Thank you

[hillegom]

+1 to sponge.
They do not like to be out of water. They cannot restart a siphon, so all the air must be out.

[Rich82]

Do they stay small?

[patpare]

No they will grow. The back glass of my tank was completely coverd in sponge