So I've got this sponge. Sold as a "Red Knob," whatever that means. I've also got a "Red Velvet," and both have been doing fine for quite a while now.

But the knob sponge, it likes to roam...

Turns out it's on a live mollusk of some sort. I was wondering why the sponge had a crack in it, with a mysterious tendency to move and then attach with ferocity.

I'm pretty pleased with this, for the most part. It's odd, and that's fun. But it does pose some questions. Does it wander around because it's unhappy, or that's just its nature?

It clearly prefers dark spaces, which are hard to get into at its size. Would a mollusk be okay on rock, or should it be on the bottom? I've got a nifty little cave about halfway up in the tank I want to try it in, but I don't want it tumbling back where I can't retrieve it.

I'm going to stick it in the sump for now. I'd rather have it in the display tank where I could see it, but I'm not sure what to do with it.


Sorry about the bad shots, couldn't get good lighting over the make shift holding tank. (No, it never touched air.)

Sponge side





Mollusk side