White fuzz on the bottom of a live rock (pictures)


New member
Not sure what this white fuzz is on the bottom of my live rock. Appears to be hairy/branchy maybe a sponge of some sort? Almost thought it was a white sea cucumber but it doesn't move. If it's a sponge, how should I get rid of it? Remove the rock and brush off? Use peroxide on the area? I read that sponges can be toxic. Thanks!
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New member
Yep, its a sign of a healthy mature tank. I have them not toxic that i know of and i have my hands in the tank weekly. No reason to remove filter feeder.


Staff member
RC Mod
I've had all sorts of volunteer sponges in my live rock---red, blue---one of those became a beautiful network of veins running from rock to rock in full light; white, lots of those. Some want the light, some avoid it. I've never found one to harm anything.


Premium Member
My vote is sponge also. While some sponges are filter feeders many cryptic sponges feed of the Dissolved Organic Carbon (DOC) in aquariums and are essential for a healthy reef. See Forest ROhwer's "Coral Reefs in the Microbial Seas" for an introduction on the roles of DOC and microbes in the health or decline of corals on reefs.