Grey Coraline Algae?

[nuro]

in the past two weeks ive noticed white/greying coraline appearign on the rocks; I've got t5 HO's that are about a year old... is this due to old lights?

 

[d-dzel]

I thought that when it turned white it was because it was dead. I bought a piece of LR pretty much all covered in purple, but it completely turned white/died and now it's starting to come back again

 

[flower]

Funny stuff coraline algae, yes I have had it turn white which changes color, or it begins like a tiny spot of color and spreads.
Gray rock... I think saltwater just turns rock gray as it ages. Watch your calcium and make sure it stays in the right range, coraline will cover all the gray eventualy. In the mean time I know the tank just looks dark and "old" I know mine did.

 

[doc308]

did you recently have water quality problems such as nitrate/-ite/ammonia spikes? have you taken the rocks with coralline out of the water? what about 50% water changes? that's the only things that have caused my coralline to change to gray. good thing is that in a few weeks it will turn purple again if the problem is corrected.