bb or dsb for aggro with rock

hey guys, just looking for a opinion. my 75 started leaking so i pulled out the fish and have resealed it, waiting for the cure time now. when i go to set it up again should i go BB or do a DSB. i had 4" of sand in there which is now in the sump/smaller 55 tank where i keep my smaller fish and inverts. probluym now is there is 9-10" of sand in there so it looks like way to much. anyways the 4" wasmt cutting it for the oxygenfree zone in the aggro DT. my levels are 0 exept no3 which is just out of control 60- 80 ppm i been doing 20G water weekly changes for 2 months now and the level is not going down. everything is alive, even found the nass snails alive in the aggro tank ( they dont ever come out affraid they will die) when i took the tank down.
my thouight was to leave the really deep sand bed in the sump and go BB in the DT so that the messy eaters dont make a problum on a sand bed. the DT is not really high flow and the skimmer is in the sump so keeping the detirus suspended dont seem like the thing to do to me but rater let it settle and clean it out, but i have to admit im getting lazy on my mantance especially now that the no3 is so high and the hunderds of gallons of salt mix ive gone threw isnt helping. what wouls you do? also i was going to put the crabs and snails back in the BB setup if i go that route to help be a cuc.