<a href=showthread.php?s=&postid=8081242#post8081242 target=_blank>Originally posted</a> by Squidly 1968 When you find out let me know. This appears to be the same thing I have growing. As it progresses, it takes on a tentacled / tendrilled appearance branching to other rocks.
No, not that I'm aware of. Most sponge grows in our tanks and seem to be limited in how large they get. Perhaps some fish will take a liking to it and reduce its mass.
The only risk to your reef is if/when you pull out the live rock for some reason and expose it to air. The sponge immediately starts to die off and when you put it back in the tank, it can cause an ammonia spike. So try to remember that if you reset your tank, and scrape off all the sponge you see - or put all the LR in a vat of saltwater to keep it submerged.