coraline algea
 

How do you get it to grow all my SPS are coloring up- But my rocks look black and coraline algea is not growing that fast-i have 3 250 SE XM 10k that I just added Was running 12K reeflux could that have caused it running 12k reeflux's ??? all params are in check-HELP

do you have any coraline in the tank to begin with? you have to have coraline to grow it. it doesnt just show up. Check your calcium levels. your sps might be using all the available calcium leaving little to help your coraline grow! good luck

Yes i have some in there and "some" on the glass but my rocks look like [profanity] they are like base rock and some are black looking tank is only 4-5 mnths old.

The black coloration might be due to a sponge or some sort of organism. Does it come off easily? Does it appear to grow?

they just look yellowish and dark black all over -and they look kind of fuzzy

I don't think I'm going to be able to id the organism, but it can apparently outcompete coralline algae for surface area. This type of problem is uncommon, but it's been reported before. I'm not sure what to suggest. A good closeup might help, might not.

The black may be a type of cyano (can be black) and the yellow fuzzy stuff green hair algae (can look yellowish under some lighting, but tough to say without an image.

Maintaining calcium, alkalinity and magnesium in appropriate concentrations would be important, as would low phosphate. :)