Black Algae?

[ekoed]

Can someone tell me what this is? It appears on the top of some of my rocks, and almost the whole top of the rocks closest to the light. It doesn't really seem to be spreading, but its like a thick coat. This picture doesn't do the color justice, but to me, looking at the tank under the lights, its looks almost black as night. My amonia is 0, and my nitrates are around .10.
i know my calcium is a little low, 370 the last time I checked. I have started Kalkwasser. The tank is just about 2 months old.

I should mention I'm feeding once a day, a little flake, and a small chunk of Reef Frenzy. I have a couple clowns, and sand sifter, and a yellow watchman gobie. One blood shrimp.

 

[Flippers4pups]

Can someone tell me what this is? It appears on the top of some of my rocks, and almost the whole top of the rocks closest to the light. It doesn't really seem to be spreading, but its like a thick coat. This picture doesn't do the color justice, but to me, looking at the tank under the lights, its looks almost black as night. My amonia is 0, and my nitrates are around .10.
i know my calcium is a little low, 370 the last time I checked. I have started Kalkwasser. The tank is just about 2 months old.

I should mention I'm feeding once a day, a little flake, and a small chunk of Reef Frenzy. I have a couple clowns, and sand sifter, and a yellow watchman gobie. One blood shrimp.

Looks like cyanobacteria to me. Syphon it out.