I keep my boas in 4'x2'x18" cages. Probably go to a 6' cage if the female reaches 8ft. My male eats a medium rat every other week. The female eats a large rat every other week. When red tails get into adulthood they can get obese fairly easy so you have to space out feedings. When she gets bigger I'd like to switch her to a small rabbit every other week to a month.