I agree, let the wild ones stay wild.
I have a basic setup, 29 gallong tank, and a 20 gallon long tank (2 snakes). the only difference is that I don't have all the climbing branches, yet. I have astroturf for a substrate, 2 hiding caves (one on hot and one on cold sides) and a water bowl. actually looking right now i noticed one is climbing up lyin on the top of the tank by the cage...lol. 
i'm going to get some braches/driftwood and such to give them both climbing spaces, and then glue some cork board along hte top back of the tank for some added grip vs just glass.
i read somewhere the optimal tank size is long-2/3rd's the length of the snake, height and depth - 1/2 length of snake. remember black rats also are going to grow upwards of 7 feet, with the longest on record being 108 inches. i'm about to purchase a biards also next week, and i'm in the process of building a very nice elaborate cage out of wood and FRP lining for them, and each cage will be 6 feet long by 3 deep by 3 high. hopefully this will be good for the rest of their lives. hopefully i dont have some mutant 20 foot snakes, lol.
hope that helps. -chris
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The reason mainstream thought is thought of as a stream is because it's so shallow. -Unknown