If a room is to be constructed for aquaria either as part of an existing building or as standing building on its own, perhaps a shed-like "Fish House" then particular attention must be paid to temperature. Alternatives exist.
Heat the room not the tanks. Beyond a couple of tanks individual aquarium heaters make little sense, it's cheaper and more stable to heat the room instead. The temperature of water is always 2 degrees colder than the air.
You could use an aquarium heater to control the temperate of and fishtank. Properly sized and properly used they are a safe and effective way to control the temperate of an individual aquarium.