Could someone identify this for me?

[JoeyH08]

I've had a 24g nano cycled and running for a few months now. My parameters are all good and I do a 5 gallon water change once a week. This morning I noticed this under a button polyp frag I've had. This is not a new inhabitant, it was one of my first purchases. Any suggestions on what this is?

 

[Devolver]

looks like a sponge to me...beneficial

 

[oscar650]

pineapple sponge.

 

[Diana A]

The white thing is a pineapple sponge

 

[SeaCucumberFan]

+1 to pineapple sponge. Harmless

 

[JoeyH08]

Cool! Thanks for the info! Will it get bigger?

 

[billdogg]

Cool! Thanks for the info! Will it get bigger?

Nope. There will be more of them however. They tend to like poorly lit areas. Great filter feeders whose population will wax and wane over the life of your tank.

 

[mcgyvr]

And bookmark this for future reference..
http://www.lionfishlair.com/hitchhiker.shtml

 

[TauntingBeef]

I bookedmarked that very nice site