Tank for a snake.?
NEVER cohab ball pythons. Not only is it stressful, but they will eat eachother. Anyway. A 10 gallon tank will work for snakes up to 800 grams in weight. A 20 gallon long will work until the snake is well over 2000 grams. 40 gallons are the biggest you'll need for a female ball python and that's only if they're over 2000 grams. Ball pythons keep themselves in small, dark spaces most of the time and while some argue that the wild doesn't have walls, our job isn't to replicate the wild. It's to make the most ideal environment for our pets. Balls are prone to stress and going off feed if they feel too exposed, amd require darkness and a lot of clutter and hides to feel comfortable. Not to mention, larger tanks are harder to keep the proper heat and humidity in.
A friend of mine had a 26 gallon tank with two pythons and they’re still doing great! Just feed them mice often and take them out gently to give them some space here and there!