Any clue what this is? Its on about 1/4 of my rock.

[Jimmye4fish]

I just started noticing this stuff about a week ago and it seems to be getting worse. Almost looks like a collection of dust. I hope someone can tell from the pics. I had a power head (suction cup) fall half way off and thought it was just sand. Obviously not! Saltwater aquariums are similar to women, once you think you have it figured out BAM you really don't.

 

[Jimmye4fish]

Also any reason why this rock is turning brown? It turning really purple and pink. Could my LED be too bright?

 

[egrape]

I dunno about the sand stuff but the pink purple growth is coralline algae! it's good, the algae you want in the tank! it's beautiful. and if your rock is turning brown, then it's probably a diatom bloom. it will fade after a water change. it's probably because of excess nutrients.

 

[Jimmye4fish]

Yeah I knew the pink and purple was coralline algae but now it's turning a rusty colored dark brown. That's the only rock doing that. Just had me curious. Thanks for the reply though!