I have a 125 with a 50 gal. sump/refug. The dt has 6" dsb and the sump has 4" of sugar fine. My cuc is various types of snails and a serpent star.The main thing is to keep the live sand "live" with all micro and macro critters possible. My tank has been set up since the mid 90's with nothing but natural filtration and water changes. It is almost all sps,a few lps,a couple clams.
Hopes this helps,