Yeah, I created a sponge filter myself. I used an old filter intake tube, you want to make sure there are holes in the tube you use. Then I put a square sponge around the tube, I cut a whole in the sponge so the tube would fit in it. Then I suck it in an old fish food container already cleaned out and such. I suck the sponge with the tube in container. Then with the remaining space i had, I put aquarium gravel, and cut up straws in. That helps store bacteria and such your filter will need, and your water will too. After that, I stuck a tube connect to my air pump, with an airstone on the other end, into the tube of the filter. Turned on the pump and the filter started sucking stuff from the water. The only problem is that it only sucks threw the top. With that in mind, I thought of drilling holes all around the container so it can suck in from everywhere.
Also, if you don't have an old intake tube for inside the sponge, you can buy some kind of pvc
pipe, but make sure you drill holes all around on it.