Black sand under top layer

I was changeing my water today and noticed under the top layer of my sand in some spots it was sort of a blackish grey color. Whats this from and how can i correct it?

 

it sounds like some waste build up.
How far below was it ?
whats the avg. depth of your SB ?

 

Well its not every were but where it is the sand in about 2.5 inches deep maybe a little more in some spots but the black part is only 1/8 inch under the top layer.

 

yes i get some of that too, i have been wondering what it is...........
bump.

 

Is it round and underneath your live rock mostly, that is where it would normally happen, forgotten why i seen it in another post...

 

well you might just need to increase your cleaner crew and watch how much your feeding so, not so much decomposes in the sand.

 

Sand sifting livestock such as certain gobies and nassarius snails will help also. With a sb that deep sand sifting livestock is not only a must it needs to be a priority. I have about 16 nassarius's in my tank and would like to get a sand sifting fish in the next several months. Just my 2 pennies...

 

Well i have had 2 dragon cobys but i think my carpet anemone ate them
but i am trying to move him to my 55 for a species only tank. No its not under my live rock its just out in the open in small patches. When i came home tonight the black that i stirred up was gone so i dont know lol. More snails i guess i got a few but not many.

 

Its just a pocket of anxious sand and that black is a sulfide pocket best leave it alone and let it just keep perking up as it has .. Don't want to uncap it to fast. Maybe point a power head to get more oxygenated water to the spot ? You are where so many are to much sand to be a non sand bed and not enough to be a DSB.. But at the end of the Day with a DSB that is always the bottom few inches and let a rock slip and some critter dig or open that up and pooof tank gone.. Nothing eats that or renders it safe .. The theory is that it will harmlessly perk up in small enough amounts to not kill the entire tank..

But at least your sand is getting enough oxygen to keep it from getting out of hand totally unlike a DSB.. A sand star may also help or get some snails to dig in there and turn it over.

 

Are these sulfides in the sand the result of adding magnesium sulfide (epsom salt) to raise your magnesium level?