For up to a year old a 12"x12"x16" tank will do just fine. Once it's taking f/t with no problems you can add more perches and move it into a larger enclosure. As an adult the minimum tank size should be around 30"x24"x24" or larger if you have the space.
ETB's will be in the ballpark of 6'+ when full grown. They are a hard species to care for, so make sure to do all of your homework before even thinking about purchaseing one.
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