She's about 10g heavier than my guy. I had him in a 10 gallon and it was WAY too small. I didn't want to have to buy an extra tank, so I went for the 40. It is really big, BUT, I have TONS of stuff in there. He has two hides, a big water dish, a little water dish, and a LOT of fake plants. It looks like a jungle in there. He seems to be okay. He eats a fuzzy rat every five days and has gained about 50g since I got him. So, my suggestion is a 40 with lots of clutter is fine if you don't want to have to buy another tank later.