Here is the basic stuff on them.
"A deep sand bed (sometimes abbreviated DSB) is a filtration method used in some saltwater aquariums. A deep sand bed, similar to the Berlin Method, is designed to cultivate anaerobic bacteria in the bottom layers of sand, converting nitrate to nitrogen gas to remove toxic nitrates.
[edit] Operation
A deep sand bed commonly is defined as a bed of fine sand with a minimum depth of 4 to 6 inches to ensure a layer of water in the lower portion of the sand will receive poor circulation. An established deep sand bed is composed of live sand which, like live rock, contains bacteria and other marine organisms such as worms, crabs, snails and stars. The creatures burrow and overturn the top 2 to 3 inches of sand in search of nourishment, which allows water circulation much deeper into the sand than would be possible without the creature's aid.
Deep sand beds can be constructed of a variety of materials, but typically fine or "superfine" sand is used, with a size between 1 mm and 0.05 mm. A larger particle size provides improved circulation, which would in turn require a greater depth. Comparatively, the larger particles may be too heavy for the worms and other inhabitants to lift, which would limit circulation into the bed. Additionally, larger particles (2 mm or larger) are prone to detritus accumulation, which would necessitate periodic siphon cleaning. A well-chosen fine grain sand will create a deep sand bed which reduces cleaning."
Your remote IMO should not be less than the 6" though.
