My substrate is a combination of live sand and crushed coral. The live sand is an argonate base. The crushed coral is not mixed into the sand completely but there forms the top layer. All together it is an inch thick, maybe a bit thicker.

Tank parameters are generally stable however nitrates seem to be a problem. I think this occurs because the sand does not get moved around enough because the sand inhabitants have to emerge above the crushed coral before being mobile.

Having the crushed coral on the top provides a good surface for ornamental macro algae to attach to and provides a good place for pods to breed. It also provides avoid surface for algae growth, my lawnmower blenny loves rolling the crushed coral bits in his mouth. Unfortunately it also prevents stirring by sand inhabitants.