use a smaller hose that has less suction power. Like Chad said try hovering over without actualy picking up the sand. You can also just stir it up a bit around the hose so the debris floats up out of the sand should sink back down because it is heavier. You could also try to get a few inverts to clean up the sand bed (ghost shrimp maybe) or even a smaller breed of loach like a yoyo loach, they love to dig and would stir up the sand for you, from there make sure you have a good filter that will turn over the water quickly.