Not sure. But I've the same problem.
Last I counted I now have about 5 LR
populated with the yellow sponge that was on one to start with.
From what I have heard this is a GOOD thing to have. Apparently you can accidently kill it off (Or on purpose) by bringing it out of water for a short period. IE: AIR is very nasty to this.
75gal Salt, 18gal Sump, Skimmer, 60lb Live Rock, 90lb Live Sand, 3 Pwrhd, 2x55w Actinic, 2x55w 10k. Guest list: Goby Green Clown, Percula Clown and entire clean up crew.