Buy a Python ...only thing that could provide enough suction to pick up the remnants of a 3 inch locust once it's gone through the digestive system of a Tiger Oscar , I tried everything , battery gravel vac , inline pond pump , all sorts , and my 5x2x2 is currently sitting in the floor so no gravity , bought the python and do water changes whilst cleaning the substrate with no fuss and no need for 20 connectors and swapping of hoses...cost me 80 on ebay but I would of paid double
I had to swap the factory suction tube for one with a smaller diameter to get the results I wanted but now it's superb I can do a small water change and cleanup in 20 mins if I want the tank poo free..