the DSB creates low oxygen zones where anaerobic bacteria can grow. these bacterias will complete the niotrogen cycle by converting nitrates into nitrogen gas which bubbles out of the sand and out of your tank,
just noticed you have a 10 gal. dont bother with a dsb. i doubt it will make much of a difference on a tank that small and it will greatly reduce the water volume in the tank.
well actually i just bought a new 29 gal tank and it is cycleing right now , but i have one big bag of sand on the bottom (live sand) , is that ok , in other words does lil sand have a positive point to?