wierd thing growing

[saltewatercrickett]

plz help me i have live rock that is constantly growing stuff allover the place and i cant figure out what this 1 thing is that grew.. it is about half inch wide 1 inch long half inch tall and yellow it fills up with water and has like 2 spouts 1 on each end and now there is another one growing next to it anyone know what this is???

 

[von_rahvin]

it could also be a sponge. I think that finding new stuf is the best part about LR and the worst part of having a bigger tank.