Looks like Moth Balls under my rocks!

any ideas on what these things might be? They're poping up under every rock in my tank.

 

Is this stuff bad? What is it?

I'm not sure what to fear but this stuff isn't very pretty, is it bad and does it have anything to do with whats in the image above?

 

Various sponges. Harmless filter feeders. In the last pic its hard to tell if it's a sponge or bleached coraline; no worries either way

 

just another sponge, you will have a burst of these and they will thin out. If you have a semi new tank you will see all types of new things.

 

Thanks!

You guys are awesome! I was getting worried. I didn't realize there were so many types of sponges. I can't thank you enough.

 

Would you happen to know how to remove the ones that are visable? Can i use a new tooth brush and siphon them out next time i do a water change?

When the polyps spread and hit an area covered with sponge will the polyp continue to spread and over take the sponge, the other way around, or will there be a stalemate?

 

Usually with those smaller white ones they will kind of grow together, then the coral will eventually take over the sponge. I had some of the white sponges in my zoa's and gsp's, it never harmed the corals, and the sponges eventually died off.