DSB in fuge

My fuge is ~2 yrs old, I have a ~7" DSB in it and I grow cheato and Halimeda algae. Works great to help keep my nitrates/phosphates down. However, recently I notice some areas of the sand are starting to get black a few inches down below the surface of the sandbed....anything I should be worried about? Just want to make sure this isn't a major problem brewing...thanks.

 

I cleaned up the fuge yesterday, tried my best not to disturb the sandbed. Vacuumed up tons of junk that was sitting on the surface of the sand. Harvested ~1/2 the cheato but I didn't have time to save all the bristle stars and pods in it.

 

My sand bed has the same black... but mine developed very quickly. My sand was heavily seeded with "old" sand from my previous tank. I assumed the black was decaying organic matter from the old sand... but that was a total guess.

Hope someone has an answer. I'll follow this thread.

 

The black is most likely bacteria that feed on hydrogen sulfide gas. Definitely do not disturb while the water is flowing. If you do something then the best thing to do is save some of the sand from the top inch to seed a new DSB. When you start the new DSB get into a habit of turning over part of the sand weekly using a tube that you insert into the sand then cover the top with your thumb until the end is above the sand level then release your thumb. This should prevent the black patches.

 

That sounds like you are turning over the sand at the deeper levels, thus introducing O2 to those lower levels. Am I misunderstanding what you wrote?