Even small spaces of organic accumulation will have measurable effects in a nano/pico, and nothing can beat the cleanliness of a bare-bottom/LR chip setup. However, sometimes its fun to use a fine-particle DSB (stated as DSB not for reduction but for its proportions in a 15" aquarium) to observe the activities of burrowing worms. There are at least ten species I can see right off the bat in the RBowl, and its amazing to watch their tracks change course in the bed during feeding time--there is truly an underworld to be found in a well-established nano DSB but it has tradeoffs...
One thing is for sure, the less sand in the system the less organic buildup you will face (because you can siphon thoroughly) and you can also feed liberally to support other life such as a small fish or two--leftover food and heavy wastes will be easy to remove at water change. DSB nanos have to be fed carefully, because if you overload the ability of the bed to slowly mineralize nutrients trouble is soon to follow. However, system biodiversity increases significantly when worm populations get a foothold in an aged DSB... my DSB is a source of continual nitrate production, but not more than 10-15 ppm continual considering protein input frequency; for my setup its worth it to have the additional infauna to watch.
