I use kitchen- and newspaper. I know of people that have raised BD's with no issues on sand, but I do not recommend it. In the end it all comes down to personal preference (I prefer to play on the safe side).
If you feed it enough, it'll grow FAST. How big is it now, lengthwise?
My baby one has grown probably an inch or two in 2 months. I also got a 1 year old male in june, he was then 12", now he's 18"+