I have magnets epoxied in the plastic lip of my 10 gallon. They are the exact same thickness as as the space from the bottom of the lip to the top and hold my metal framed mesh screen in place very well. Bought the magnets in a pack at Home Depot for about 3 bucks or so. Use them all or as many as you can evenly space around the lip. I've got one corn that constantly cruises the top looking for a way out, but I haven't had an escape yet. Will post a pic of aquarium top so you can see.