I'm gonna say no, not a good idea. If the tank has a frame on the bottom, the weight is carried through the four corners and none of the corners should be overhanging the stand. If it's a rimless tank, it needs to be supported underneath with nothing hanging over. It might be possible to have a sheet of plywood cut that matches the size of the tank. Then you can sit the tank on top of that with the stand underneath it. I don't think you would want to do that for a really large tank, but it might be ok for a 20 gallon.