Some Live Rock was Purple now turning black...new tank.

[I Love Coral]

What does this mean?

[NanoTX]

Probably Cyanobacteria (http://www.ucmp.berkeley.edu/bacteria/cyanointro.html) . Bad stuff. Suck it out.

[Randall_James]

Cyano in a new tank? does the black stuff blow off the rock easily? And what kind of rock is this? Tonga is famous for this black stuff (is some type of die off)
Cyano is more a problem in more mature tanks, I have never seen it in a new tank.

[I Love Coral]

http://reefcentral.com/gallery/data/500/106617Live_Rock.jpg

[milhouse74]

Die off and diatoms. However I will add, I only had cyano problems in my tanks when they were under 6 months of age. It doesnt look like syano from the pic.

[I Love Coral]

Should I worry much?

[milhouse74]

Nope, if your having die off of coraline i wouldnt worry too much, there are many types that dont survive well in tanks. You will end up with what can in time. New tanks will go through a few weird stages.

If it is cyano, I would worry a little. If it gets to spread it can be a real pain. Go get yourself a new baster (like the kind you probably used on your bird today) and try to suck the stuff up. If it is Cyano (doesnt look it from the pic) you want to suck it out. It will be a super deep red, and start out in your places of less flow.

[I Love Coral]

When I rub the rock there is some bright green algae developing underneath the black stuff.

[milhouse74]

Green coraline, and a pinkish purple can survive in your tank. Is it a HARD green algea, like calcified?

Also when you remove the stuff there is it kind of dusty, or does it hold together more sheet like?

[I Love Coral]

Dusty.....brillant green..not sure if it is a hard algae...newby here sorry

[Randall_James]

Blow off the black stuff, and the brilliant green stuff is precurser to other coralines IME. I like the green but the red/purple coraline is more aggressive and wins out. I would not worry much about it.

[milhouse74]

Yes, if the black stuff is dusty, thats god news. It is likely die off and not Cyano.

You can tell if it is hard by touching it, does it feel like it is just the rock? If so it is a coraline, and it sounds like it is.