I have a male BP, about 15 months old. He currently measures exactly three feet long, weighs 830 grams, and is housed in a long 20 gallon tank. From what I've read, it sounds like he probably doesn't need a bigger tank right now, but will before too long. And even now, I feel like there isn't enough space. He keeps knocking one of his hides into the water dish, and there's barely enough floor space outside the hides for him to move around.

So my question is, what size should he be upgraded to that will be large enough for the rest of his life? I've read anything from a 20, which is obviously going to be too small, up to a 55, which seems too large. This is my first and only snake so far, though, so I'm a bit clueless!