Branches just slightly larger than the animal's diameter must be provided for climbing. Young iguanas can be kept in smaller encloses, but the smallest size recommended is a 55 gallon aquarium. There are no manufactured aquariums on the market today that are large enough for an adult iguana, so the only real choice is to home build or custom order a cage. Many companies who advertise in reptile trade magazines can build good custom cages of appropriate size. Proper substrates include newspaper with soy-based ink, bark chips, and Astroturf.
Newspaper is by far the most practical, although the least aesthetically appealing substrate.
Do not use wood shavings, corn-cob bedding, sand, or crushed walnut shells in iguana enclosures. The other substrates are not digestible and can cause severe intestinal blockage if ingested. Iguanas are from tropical areas, and require rather high relative humidity to shed properly. More than one home fire has been started by a wily free roaming iguana that knocked over it's heat lamp. Free roaming iguanas also mean free roaming salmonella bacteria, which should be avoided at all costs.