Hello, I have a couple of pleco tanks, I've found a thin layer of fine sand is pretty good for hovering the mountains of ****e off, it just sits on top. These guys have said all the main points - filtration, oxygenation and territories. the last one is very important with more aggressive species like large panaque and pseudacanthicus. Also its quite a good idea to have high circulation/flow in the tanks - it's more natural for the plecs and it tends to keep waste suspended so it dosen't collect in dead spots - I use low pressure marine pumps/powerheads for this. Also try to avoid eating meat eaters (pseudacanthicus/ leporacanthicus) and wood eaters (panaque), panaques that get too much protein can develop digestive problems. Here's a picture of on of my tanks -