Necessary for the operation of a DSB, live sand is sand that contains the invertebrates - critters, detrivores, etc. - that turn over sand and consume waste products. It is the invertebrates that make it live sand, not the sand itself (which is just an inert, inorganic mineral).
What is live sand?
Live sand is abundant with bacteria and micro organisms that consume organic matter and waste and in turn provide a natural food source for tank inhabiitants.
Typically, live sand that is purchased is coral sand that has been collected live from ocean water reefs ot aquacultured.
Dry sand will become live if seeded with a sample of sand from mature a reef aquarium or cultured from the addition of live rock.
Seeding non-live sand
It would be cost prohibitive to start a new marine aquarium with 100% live sand or even 50/50 live/dead sand. In most cases hobbyists that start a new tank will seed dry sand with sand obtained from a fellow reefers mature tank. Greater diversity can be gained if live sand can be sourced from several mature systems. It will take time for the sand bed to establish, but simply obtaining a cup or two of livesand and spreading it over the new sand bed will start the process.
Care needs to be taken when choosing the source if using the seeding method, the sand could be diseased or have chemical contaminants if sourced from a tank used to hospitalise or medicate livestock.
- Do i need live sand for my tank? - Marine Depot
- What Live Sand Is and How It Is Used in a Saltwater Aquarium - About.com: Saltwater Aquariums