What is this?

[chevy4w]

Wondering what this is.

 

[duberii]

Does it come off the rocky easily? If so, it's probably cyano or some type of pest algae. If not, it could just be coralline (good type of algae, shows that your tank is doing well and your parameters are stable).

 

[chevy4w]

It doesn't come off easily when I tried to blow it off with the baster.

 

[KrisReef]

The brown stuff kind of looks like a sponge with all those holes?

 

[duberii]

It doesn't come off easily when I tried to blow it off with the baster.

Looks like Coralline algae then- Don't worry about it. It'll probably take over your rock work in some time, but most corals don't mind if they're healthy. If you really hate it you could get a sea urchin (just make sure your tank is well established, which it seems to be because you have these big patches of coralline), since they plow through coralline like it's nothing.

The brown stuff kind of looks like a sponge with all those holes?

It could also be a sponge- you might have to go in and feel if it's soft or hard. If it's soft and, well, spongy, then it's a sponge. If it feels like it's part of the rock, it's coralline.

 

[raketemensch]

I second the urchin -- I've got a tuxedo urchin in a tank here, and s/he's enormously entertaining with his huge afro constantly picking stuff up and carrying it around. The rate it plows through coraline is amazing.

I had to rescue the ammonia badge from him the other day.