I hit on this point in a thread I made about getting a Denitrator/Nitrate Reactor.

My question is: does anyone have a deep sand bed in their tank (4-6 inches deep)? If so, how are your Nitrate levels? I had toyed with one when I had a 120 gallon tank a while back, but it was roughly 3 inches deep. My nitrate levels (with a very similiar bio-load) stayed around 30ppm doing a water change once per month. Crank up the tank size, only 1 more fish, sand bed is about 2 inches deep, and if i go a month without a water change (only did once) and the Nitrate went well over 160ppm.

That alone makes me believe that the deep sand bed does work, if it's deep enough to give the bacteria that can't live with oxygen present enough room to breed. So does anyone here have a deep sand bed *AND* see a drastic reduction in Nitrate levels?

Also, i've read several places that the sand particle size should be no smaller than 0.05mm and no bigger than 0.2mm in diameter. So if anyone here does have a deep sand bed, and it is working, how fine is your sand?

no deep bed for me, tried it, but if u touch it in any way u get shit floating every where releasing nitrates ect into the water.
but in a fuge, great, because u dont have to touch it