Veiled chameleons are arboreal animals that live their lives moving through branches, so vertical space matters far more than floor area. An adult male needs a tall enclosure — height in the range of four feet is a sensible target — to allow the natural up-and-down movement that supports both exercise and thermoregulation. A short, wide tank designed for a terrestrial reptile is fundamentally the wrong shape for this species.
Females, being smaller, can be housed in somewhat smaller enclosures, but the same principle applies: taller is better, and bigger is rarely a problem as long as the animal can still locate its basking spot, food, and water within the space. Cramped enclosures contribute to stress, poor appetite, and chronic health problems.
Veiled chameleons are strictly solitary. They should be housed individually, as cohabitation reliably produces stress, aggression, and injury even between a male and female outside of brief, supervised breeding introductions. Any guidance that suggests keeping two together in a shared enclosure should be disregarded.