after trying a deep sand bed, it sounds great in theory but in practice its just annoying. I love a sand bed so I've done 2 different ways now. I like just enough sand to cover the bottom, like 1/2'' or less. Or I have also started using a plenum in one tank and I am pretty happy with that as well. If denitrification is what you are looking for, its better to just do some carbon dosing IMO.