Can animals be placed in a terrarium?
It is possible to create realistic set ups which include animals often called vivariums. Small animals like spiders, centipedes, insects, frogs, very small lizards can be included. [Perhaps small fish if you have a "pond" as part of your set up.] HOWEVER, DO YOUR RESEARCH! If you are going to try to keep an animal in your set up, make sure that it can comfortably live in that environment. That includes living space as well as food, temperature, moisture and other conditions. Do not ASSUME the animal will be able to happily live in your setup. For instance, most animals will require that some sort of supplementary food be provided for them. As another example, many animals sold in pet stores are juveniles and will, perhaps rapidly, outgrow your terr. I cant say it enough -- DO YOUR RESEARCH!