Deep sand beds work until they don’t. Methane can build up and then a rock falls or it gets disturbed somehow and the Methane bubbles are released and nukes your tank. DSB have been out of vogue for a while, just like undergravel lifters, and wet/dry filters, they all work (or work for a while), but more efficient and effective filtration/nutrient export methods have beed found.I did a lot of talking to friends who have been in the reef hobby for a long time and watched father fish and asked him a couple things, he swears by deep sand beds because there is evidence about the health of the sand bed in the 1st 10” or so directly correlates with health of the reef. I’d probably do 1” of mud 2” of sand then layer a bit of rubble of shells and crushed coral