A deep sand bed (sometimes abbreviated DSB and also called a "plenum") is a filtration method used in some saltwater aquariums. A deep sand bed, like the Berlin Method, is designed to cultivate anaerobic bacteria in the bottom layers of sand, which can convert nitrate to nitrogen gas, thus eliminating the toxic substance from the water.

A deep sand bed is generally defined as a bed of fine sand at least 4 to 6 inches deep. This depth is necessary to ensure that there will be enough water receiving poor circulation. An established deep sand bed is actually made up of live sand which, like live rock, is full of bacteria and other marine organisms such as worms, crabs, snails, and stars. These creatures dig through the top inch or so of sand in search of nourishment, which helps circulate water much deeper into the sand than would be possible without their aid.

Deep sand beds can be made of any material, but typically fine or "superfine" sand is used, having a size anywhere between 1 mm and 0.05 mm. A larger size might allow for better circulation, which would in turn require a greater depth. At the same time, the larger particles could be too heavy for the worms and other inhabitants to move around, which would limit their ability to help. Lastly, very large particles (2 mm or larger) are very likely to accumulate detritus, which would necessitate periodic siphon cleaning. A well-chosen fine grain sand, on the other hand, will create a deep sand bed which may never need cleaning.

External links

• Marine Aquarist Association of South Texas (MAAST) Forums dedicated to keeping marine aquariums.
• An Introduction to Deep Sand Beds
• http://www.reef-eden.com/DSBs.htm