Best tank I ever saw had a 4" substrate with the first 15-20% being crushed coral and the back 80-85% being live sand. This guy had moorish idols, leopard wrasses, and multibarred angelfish among others in his 500 gallon.
I'm tempted to try it in a 55 later on, though with much less finicky livestock haha.
Display tank - 24g nano w/ softies/montipora
I run electrical appliances underwater and enjoy injecting things with Kalk filled syringes.