I was cleaning out my tank when the idea came to me of making a homemade canister filter. I thought of some simple ideas to construct it, and I wanna run them by you guys for insight. Here's a simplified version of how I'm building it: Get a 2 liter bottle and drill 2 holes on the side, near the bottom Drill 1 hole in the middle of the cap, cap the bottle Put tubing in all 3 holes Seal all holes to make them airtight Fill bottle with filter media Here's how it works: Dirty water will siphon from the tank into an intake tube, which will run below the tank into one of the two holes near the bottom of the bottle. The dirty water will run upwards through the 2 liter towards the cap, being filtered by mechanical, chemical, and biological media through its course. The other hole near the bottom has tubing connected to a powerful air pump, which will produce bubbles that flow towards the cap. As the water passes through the media, it will hit the cap, which will have a single hole with tubing. The bubbles from the air pump will push the water through the hole in the cap, which is connected to tubing that relays the filtered water back into the tank. My only concern is the bubbles. Will the bubbles actually PUSH the water through the tubing with enough lift back into the tank? I know I can use a pump or powerhead, but I'm wondering if bubbles will provide enough lift. The whole system is airtight, so the only way for the oxygen to escape is through the cap, which should push the water along with it. I'm unsure if it will actually work- will the bubbles carry the water or not? Tell me what you guys think before I build it.