I did this for a 10 gal. But I did not use a hinge. I used an Aquaclear filter and a single piece of glass. On the end of the glass where the filter was, I used two pieces of back strip to fill the gap between the glass and the end of the tank on either side of the filter. I considered two pieces of glass and a hingle, but that seemed rather much for a 20 inch long tank. On a longer tank I would consider hinging it.