If it's a normal BCI male (which he looks like he is to me) then you're looking at him being around 5-6ft and around 20lbs as an adult. There ARE cases of BCI's growing larger than the average, but they're definitely not the norm. An appropriate-sized rat every 2 weeks will be just fine for him.He'll end up however big he'll be no matter what, it's just how long he takes to get there is what the feeding schedule/diet does.