To be honest, I'd play it safe and actually never use sand as a substrate - it just totally eliminates risk. Sand can be dangerous in a number of ways, anywhere from running impaction risks to causing bacterial issues with your dragon. I use reptile carpet, it's the easiest substrate to use and Leyla doesn't mind one bit. I vacuum it out every time she goes to the bathroom and wash it once in a while, piece of cake. No scooping, no changing sand. Plus, sand can actually 'stain' their feet and bellies, I'd personally rule against it. A lot of people who really get into the vivariums also use ceramic tile or linoleum, you could play around with those as well.