What is this....

[mwbeach]

Not sure what these are. About the size of an eraser

 

[redfishbluefish]

It's awfully fuzz and blue, but I'm putting my money on them being feather dusters.

 

[mwbeach]

I just googled that and it looks the same. They shot back into something and closed up when a fish came by.

Are they good? Bad?

 

[redfishbluefish]

They are a nice little filter feeder....they do no harm. I'd love to have them in my tank.

 

[mwbeach]

Thanks. I just noticed them today on one rock. About 6/7 of them right now