Grey Sand

[grussell]

I think others have inquired about this. I have a DSB(4-5 inches)of fine sand from Marco Rocks. 75 Gallon Tank. The sand was not live, though I seeded it with 2 cups of sand from my LFS. There are now three places against the front glass where the sand is turning grey--NOT BLACK. These are coming from the TOP, at the surface, and spreading downward and outward from there. Any thoughts on where that comes from? The spots are continuing to grow. I may be able to post a pic tonight if needed. Hoping someone just knows what this is. Cyano or something?

[grussell]

Should add, tank is only 5-6 weeks old--though it is cycled. It has excellent flow(a little too good--I've got all kinds of hills and valleys in the DSB now. )

[cloak]

I don't know what might be causing this, but in a tank that's only 5-6 weeks old, just stir these areas up with your finger or a stick. (preferably right before a water change) It could very well just be an accumulation of fine dust from the sand. If it keeps coming back though, (over & over again) then I would start looking for answers. GL.