If it is not already in the tank, I would recommend Krylon clear polyurethane sealant.>Some have even used it in their fish tanks without any problems. Or you could use GE 2 clear 100% silicone. Make sure to get the window and door, not the bathroom kind. (It has mold inhibitors that would be poisonous to the frogs.) It is as safe as aquarium sealant but cheaper. I heard it will leave a hazy finish, so that is something to consider. I hope this makes sense. I am very tired!