The reason why I selected these boulders to be included in my zoo enclosure is because they blend in. As you can see in the above picture, they live in grasslands, but they also have large boulders. These boulders can be used to give them leverage to reach higher grounds in order to keep their families safe. Another reason is that if they weren't captured animals, they would be facing boulders such as these. Why not make they're zoo stay more realistic? The only thing I want for these animals if for them to be as comfortable as possible.
This is the dirt I will use for their zoo enclosure (if you ignore the house to the side, the picture illustrates this perfectly). This dirt will be close to their habitat's dirt. The dirt is hard and packed, but they can still dig into it to make their dens. This way their instincts won't get them hurt in the process of digging into impossible dirt, or their den caving in on them. This will create safety for these animals and the home that they need in order to survive.
What do they eat?
Meerkats are foragers, meaning they have to find their food. The food that they mainly eat are insects, which they dig up from the ground most of the time. They can also eat, however, small vertebrates, eggs, and plants. If you wanted to keep them healthy I would say you feed them a lettuce head. (Keep in mind there is little information on the web for feeding household meerkats. I've been looking for half an hour and I can't find anything. I heard that they feed them lettuce though, but that is all.)