yea, sponge. great looking sponge. 90% of the 'color' on he rocks is sponge. too bad it is one of the least likely things to survive.
I'm on day 6. still doing water changes. there are about 4 places where i have what looks like white mold developing. kind of looks like what one of my zoathid colonies had in my nano. then it was attributed to melting syndrome or something like that.