ID please!

[dammar]

iv got like 4 of those growing out of some LR iv had in my tank for about 4 months now, they just appeared recently. it looks like a kind of sponge or something maybe? iv no idea =/
its about the size of a penny

 

[trippkid]

I would say you answered your own ?. Definitely looks to be a sponge of some sorts.

 

[reefkprz]

definatly a porifera (sponge) this one I am familiar with though I couldnt tell you the exact species name, it is a 99% reefsafe, filter feeder. since it loves dark corners it usually doesnt encroach on corals. and that is about the only danger you would face from this type of sponge. or maybe a silicious or calcerous splinter from the sclerites if you were to poke it hard with your finger.

 

[royal gang]

Sponge.