Clearseal clear plastic condensation trays are designed to fit on to all glass aquariums. Their purposes are to stop fish or other habitants from getting out and to reduce water evaporation. They incorporate a neat little feeding flap and are available in 4 sizes each 12" wide. Most modern aquariums no longer need these, but they are useful for breeding, hospital, and quarantine tanks. As they can easily cut into different sizes or shapes, they can be converted into sump covers too.