Here ya go. Some plexi glass, hinges, rivets and sealant, a latch to close it, and a drill for the vent holes.





This way you'd have an enclosed cage. You get an under tank heater that takes up about 1/3 the bottom on one side, a good thermostat to control it, a digital thermometer with probe to monitor it, and there ya go. No issues.

I guarantee if you use such a large fish aquarium you will be miserable. You'll never be able to keep it the proper temps or humidity, and you'll get tired of trying to reach all the way to the bottom to clean it.