Black patches coming through the sandbed


New member
I've been searching the forum for sometime trying to see if anyone has dealt with what I'm dealing with, but haven't found much.

I've been getting patches or layers of black, maybe algae, under the sand bed. I'm not sure what it is. It's not slimy. It doesn't start on top of the sand bed. It just starts to clump up and eventually raises up becoming noticeable. When I vacuum it out, it comes up like a sheet of paper. My water parameters are great. My pH sometimes creeps up. I'm not completely sure why.




And, I'm not sure if my lights are on too long. My blues start ramping up (apex controller) around 730 and are on completely by 9 and are turnoff at 9pm. My whites start ramping 30 minutes later for 2hrs and then stay on till 830p. My high noons (equivalents to MH) come on for about 5hrs. That's my light cycle.

I'm running a brs carbon/gfo reactor and a skimmer.

Any ideas what the black stuff is?


New member
Sorry for the pic quality. I took them with my iPhone.

One the first one you can see the clump.

The second one you can see the clumps coming out of the sand bed behind the sps.

The third one is just another angle of the first pic where you may see it raising.

Hope that helps.

I appreciate any input.

BTW: I have not fish in the system yet. Just corals and inverts, CUC.


Master of Space and Time
That is anerobic bacteria breaking stuff down and holding hydrogen sulfide. You can get sand sifting critters to churn stuff up or vacum the stuff out. When you disturb your dsb you are releasing all kinds of stuff into your water


New member
Ok. So the tank is ok? Not an algae outbreak necessarily?

I bought a sand sifting starfish and a few nassarius snails yesterday so we'll see.