I have a coral reef aquarium (180 total gallons).
I lost TONS of money on live coals! (I get mad when I look back now)
So I got a RO/DI unit, and now I use it for my snakes.
I only give my snakes RO, not the DI. (they NEED the electrolytes).
Here is a good one. (and you don't need a DI unit, so it will be even cheaper!)
http://www.bulkreefsupply.com/store/...my-system.html
Its not much at all, you get CLEAN, SUPER CLEAN water. (I use it for my drinking water aswell, only the RO.)
Then you can get a In/Out TDS meter. (to know when to replace your filter media)
http://www.bulkreefsupply.com/store/...m-digital.html
Not bad if you ask me, it is less than low end snake.
Or you can get a cheap chinese unit, it will be good enough for a snake.
http://cgi.ebay.com/Aqua-Reef-RO-DI-...item588a2ac410
http://cgi.ebay.com/100-GPD-Drinking...item2a0a3fcea2
http://cgi.ebay.com/Portable-Mini-Re...item20b41eba7f