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Is this a brand new enclosure with an unopened package of sand? If it is used sand or calci-sand throw it away immediately. If you can't afford the $10 (usually less) for a substrate how will you be able to afford to care for any snake?? There is weekly feeding, supplies (temp gun, heating source ~flexwatt or heat pad~ snake hook, supplements, vet visits, cleaning supplies, etc). If you can not afford an alternate substrate to the point that it is the determining factor in if you get a snake and what species to get then you really can not afford the snake. They are not as cheap to care for as most people think and purchase should not be based on something as trivial as being unable to afford a proper substrate.

~Add~ If it is simply an issue of not buying a different substrate right now you can choose just about any species you want, use paper towels for now and decide on a substrate later on.

Kenyan Sand Boas are cool little snakes, diet of rodents, fresh water daily, few inches of sand or soil/sand mix, 80-85 for temps, basking temp of 90ish, heat via heat pad. Thesse guys range from 18 to 28 inches +/- a couple of inches as adults.

If your terrarium came w/ calci-sand throw it out.