Africans love sand! Some peacocks apparently have a sensor they use when they hover over sand to detect little critters in the sand. Its pretty neat... so useing sand would bring that ability out!
the sand is heavier than poop, so you can stir it up a teeny tiny bit and take out the floating poo bits, or be ready to pinch the tube for the cleaner when you clean the sand, enough so that the sand falls back down but the poop keeps going. might be able to experiment with the amount of suction necessary just for the poo, and put a clamp or something on the tube so that there's not enought suction to pick up the sand. aside from that, just rinse out whatever sand you suck up and put the cleaned sand back in the tank.