If no food is getting to the bottom of the tank, you need to feed the catfish. Mine rarely go higher than about 3 inches from the bottom of the tank.
I feed mine sinking catfish wafers. I also soak part of my flake in tank water so it sinks, as my rams like to eat from the bottom as well.
Getting back into the hobby... restocking a 55 Gallon tank with peacock cichlids (currently housing 2 synodontis petricolas). Planning a complete overhaul of my 30 Gallon Oceanic Cube (currently housing a bristlenose pleco and a praecox rainbow).