I am new to tortoises and just got my RT last week, named Yuri I read everything I could find and finally decided on a sand, dirt and pellets for the substrate. Petco does not recommend sand because the tort might accidentally eat it and so I won't use it in the future. My question is how often to change the substrate. I have been able to pick up his 'mess' or he has been going in the water when I've soaked him so the substrate is staying clean. Also, I have been feeding him once or twice a day and he eats it all. He loves the spring mix and carrots. How long can he go without eating? I had a Florida Box Turtle and he sometimes went several days without eating (mealworms). Any help you can give me is appreciated. Thanks. And lastly.... how can you tell how old he is?