What is this?

[pulpfiction]

I Picked up a live rock and theres a weird thing growing on the bottom. please help id?



There are some bright green things too.

 

[terraincognita]

Sponges harmless filter feeders.

 

[Teen reefer]

Sponge it won’t hurt anything and are good filter feeders.

 

[pulpfiction]

Very cool. Thanks all! I never saw anything there before then a couple months later i flipped it over and boom, giant thing on the rock lol.