How it works is the air from the pump travels to the center of the sponge and then rises through the lift tube which draws water through the sponge and out the top. The sponge does a little mechanical filtering but mostly its a great place for biological bacteria to grow. Very simple, works awesome, and lasts forever. I think the ones I mentioned earlier may be a little difficult to set up and the simplicity of a sponge filter may be the best option. Search xy-2835 sponge filter on amazon, Another one that I know is smaller so it wouldn't stick out so much.