I consider my DSB to be my "filtration system". It is held in the middle section of the sump and has a surface area of 62cm (25") by 23cm (9"). The depth consists of two distinct layers. The lower 5 cm (2") is CaribSea Aragamud, whereas the upper 7cm (3") is a mixture of sands from my previous tanks and is mainly TMC oolitic sand and Aragamax.

UPDATE (Aug 01): The DSB/Refugium now contains a variety of macroalgae. It is worth noting that even using Merck Professional Test kits, both NO3 and PO4 are undetectable.

I generally feed the DSB every day with one cube (say around 1cm or 0.5") of a frozen food. The frozen food is just a finely blended mixture of normal aquarium foods, the last batch consisted of brine shrimp, lance fish, Vibragrow, ESV spray dried phytoplankton, mussel and a little Marine Lipids which are sold in some chemists (drug stores) nowadays. I do not bother to defrost the cube, just put it under an old oyster shell I keep in the sump. I tend to move the shell around, day by day, in order to encourage a more even distribution of "critters".

UPDATE (Aug 01): With the sand bed pretty much stable, I now rarely directly feed the DSB.

The worm population does seem to be fairly large!