I am new to owning Russian tortoise and still trying to figure out best substrate for her indoor enclosure. She is around 5 years old. There are so many options that work from what I read but it seems like a lot of people really like Orchid Bark. Is this the best choice? Also do I just buy it from Home Depot (like one meant for Orchids) or do I need to buy one at the pet store specifically for reptiles? Should it be organic? I also see there are different sizes of chips.....Any help would be greatly appreciated.