Incredible video. Thank you so much for sharing.Because most Parachromis are consummate diggers, and tank redecorators, whatever you use will need to be heavy enough to quickly fall back to the bottom.
If using sand, Pool Filter Sand fits that bill, its dense enough to be backwashed.
Play sand or other light weight sands will tend to drift with water flow, and get sucked into filters and can be destructive to impellers and the like.
Below is a video I took in their natural habitat, for tank-scape ideas.