What is this algae?

[Wolf89]

What is this algae? Tangs seem to be keeping it off the rocks, but it's all over the overflow box and sand.

 

[Bret Brinkmann]

It looks like gha with detritus mixed in on the overflow. The stuff on the sand looks like a mix of several things such as diatoms, detritus, and maybe some cyano.

 

[BayouReefer]

I would say GHA also

 

[Saltycrew]

Get a good clean up crew (turbo snails and scarlet crabs) should clean it right up