Can you take the "vac" part off? Just use the tube, that should get it up. When I did my first cleaning of my CC, I was sucking CC and sand and clogging it up, but fish waste should be easier, smaller hole stronger suction (never took physics, so I might be totally off). Unless some one else has a better suggestion. Not to sure if the further below the tank would cause more suction or not (I know that was bad grammer, but couldn't think of how to reword it...)