It is supposed to allow for anerobic bacteria to colonize and help in consuming nitrates/nitrates. It seems like it is a trap for uneaten food and waste, and would be a larger problem then a solution. There are other ways to go about enacting a DSB with out the issues listed about, like a 5 gallon bucket full of sand and a trickle flow being run across it and then pumped back into the aqaurium. Some what similar to an algae scrubber.
A DSB in a tank is a detritus trap. If you are going to do a DSB its best to have it with a rigirous flow system, sumped in with your tank, but in a different tank. There are a lot of DIY's on the internet describing that, read it in an old fish magazine a couple days ago. I dont know. Seems more effort than it is worth. Who knows. Give it a look.
If interested read this, its an extencive articel (and a book is listed) that tells you how to set up a DSB the proper way, though it will never be as pretty or as clean looking as a standard sandbed.
