first off, you must quarantine the new one for at least 30 days. Giving you time to get it to the vet to make sure it won't infect your current bp with anything it has. I honestly wouldn't recomend putting the two together for the fact it coudl stress your current bp out. But depending on how old it is, its up to you. I would probably go with a pretty large enclosure. Maybe a 55 gallon? with 4 hides.