Hi, it`s good you`re pleased with the monitor, they truly are wonderful animals!
If you provide a means for them to defaecate in a water dish/pool, they usually do!
Sleeping soundly through the night isn`t a problem either, so long (obviously) as the animal`s active/eating normally etc, at other times.
The problem with fish taks is the ammount of heat you lose through the glass, also, no privacy. A "quick fix" (temporarily), is to tape some thin plywood around the back, two sides and bottom, to help insulate. You haven`t mentioned substrate, what type and how deep is it?