Gila Monsters make hardy, undemanding captives.
Adult Gilas can be maintained in aquariums, large plastic containers, or custom cages. Adults should have a minimum of about 0.3 square meters (3.125 square feet) of floor space. In the wild, Gilas spend most of their lives inactive and underground, so large amounts of space are not required in captivity. The cage should be large enough to provide a good thermal gradient—warm on one end and cool on the other. A lot of cage height is not required.
Some people maintain Gilas in groups in larger cages. However, individual housing facilitates feeding and maintenance. In the wild, Gilas are usually solitary animals except when they congregate in the spring for mating or in the winter for hibernation in communal areas.
Cage substrate can be as simple as newspaper or wood shavings. Many substrates commonly used for reptiles will work. I use Sani-Chips®, a chipped aspen bedding product. It is inexpensive and very easy to spot clean. In addition to regular spot cleaning, it is a simple matter to totally replace the bedding periodically.
In order to create a temperature gradient and allow the animal to thermoregulate, under cage heating (such as Flexwatt® heat tape) should be provided for a portion of the cage and controlled with a thermostat or a dimmer switch. Maintain a basking spot temperature of 30 to 32 C (86 to 90 F) measured on the substrate over the heat source. For animals preparing for the breeding season, a good range of temperatures is beneficial. I prefer a larger range of temperatures, from about 24 C (75 F) on the cool end to 33 C (92 F) on the hot end. During active periods, Gilas typically maintain a body temperature of around 30 C (86 F).