So my idea is to use eco complete on top of the filter plates, and then a layer of aquasoil, and then a cap of sand, for a total of 4" or 5" inches. I once did an undergravel with just eco complete and aquasoil (ADA) and it seemed to work great while I hadn't, which admittedly was only a few months before I had to take it down for life reasons. I know the layers, plus the mulm on top, will eventually become one, but will that be a problem?
The reason I want the sand is I think the botanicals would look nicer on top of sand than just dark aquasoil, and because I plan on having fish that like to play in sand. Thank you for reading.