Sand Turning Black

How do you stop the sand from turning black. I know its bad and all but what do i do to fix it? 3in of arg in there now mixed sizes. i think in stuck a the hopeless middle ground of sand hell. How do i fix this problem any suggestions?

 

Hmmm, my sand turns red / black but when the power head is blowing water right above it, it goes away.

 

how bout some pics and more tank info partner

 

Pics of Tank

dont know all the specs.. acquired tank. its 110 gal with maybe a 15gal sump/wetdry.open loop. also in there bioballs, skimmer. two powerhead to keep the water moving in a loop.. across the top off the tank bank the the glass and return along the bottom. sand is about 2.5 years old. have been adding smaller substrate .5cm at a time. heard a variety of substrate was helpful.

 

I think you'd be better off if you change all the crushed coral out for sand

 

I've had a similar problem happen. My wasn't as bad and it wasn't as dark, but some of the larger pieces of my substrate turned a dark green. I believe it was algae that was growing on it. I added some more finer substrate and that helped.

 

The depth of the bed (and particle size) are critical to provide the correct conditions. If the sand bed is not deep enough, and the oxygen level does not drop enough, the sand bed will produce nitrite from the nitrate. A disaster. Conversely, if the sand bed is too deep, the entire bottom of the bed can turn anoxic and produce sulphur dioxide. If this happens the affected sand turns black. If this black area is disturbed or sampled it releases the characteristic rotten egg smell. This chemical is of course toxic. However in practice, it is not a problem in a few very small and isolated spots . Larger areas obviously leach enough sulphur dioxide into the water to poison and destroy the rest of the sand bed, and soon afterwards the rest of your livestock.
heres alink to the rest of the article.
Deep Sand Beds