I know and read that mixing species of tortoises is not recommended. Is it really that big of a deal to mix species as long as their living habitats are similar? I have a baby Greek tortoise which i was thinking about getting him a friend. But I was contemplating getting a baby Leopard tortoise. Will that cause any major problems? Ive read that they are not very aggressive species. What kind of problem will i run into if i have them living together?