Re: need better heating...
Glass in fish tanks are not an insulator. If it was acrylic it would have more insulating properties but still not as good as a tub that is the right size for the animal. If you still want to use a tank then go to home depot and in the isle where you have insulation and foam panels they have a foam style 4x8 sheets of hard foam insulation that is used for insulating between vynil siding and plywood. Its made by dow and is blue on one side and foil on the other with foam in the middle. Its cheap. Get that and cut it to match the sides and the back of your tank. You can also cut a piece for the top of the tank leaving an inch gap on one side for air. You can easily attach it to the screen top on your tank. This will stop the thermal transfer from the glass and insulate the tank well. Use a hot glue gun or foil tape to adhere the insulation to the outside of your tank.