That's how I use to clean ugfs - I would move the gravel awy form the base of the lift tubes, pop off the lift tubes and shove a siphon tube in the hole and get as much gunk as I could. I only have 2 tanks left with ug filters in them - and I'm going to be getting rid of one of those. I had my best luck using ugfs with smaller, lightly stocked tanks. They do keep the water clear. But, you have to break them down eventually. And when they go out of wack, its a pain to get them caught up with the load again. Now I use mainly Aquaclears or canisters for my show tanks and good old box filters for my breeder tanks.