[Geogal17]

hmmmm...i have the sand sloping form the back so that its about 3 inches deep in the back and about 1.5 in front. I have a horseshoe crab and fiji star that keep the sand pretty well stirred up in the front, its in the back part where the sand is deepest that i've started noticing the sand at the bottom is turning black/dark grey. Is this because it gets less light or because nothing is cirlulating air/water down there?

So far everything else in the tank appears to be going alright.
All tests are within normal ranges.

I was just curious if this was a bad thing or not