The word "vivarium" has its roots in the Latin word "vivere," to live. In a broad sense, a vivarium is a habitat for a pet -- technically, a bird cage could be considered a vivarium. However, a vivarium is usually used to describe a terrarium housing small animals.
An Accidental Discovery
In the 19th century, a London surgeon accidentally created a garden in a jar when he buried a cocoon in damp soil in a glass jar. When the soil sprouted a fern and grass, he lost interest in the moth he was waiting for and focused on his sealed, self-contained garden. Since then, terrariums have captivated people as miniature examples of an ecosystem at work.
Terrariums are essentially miniature greenhouses that replicate natural environments for live plants. These little gardens are contained in a transparent, sealed container where water, plants, soil and air combine to work through the natural processes of photosynthesis, respiration and water cycling. Moisture in the air condenses on the walls -- usually glass -- and returns to the soil where it's absorbed in the plants' roots. The plants emit gas, which is turned into liquid in the form of condensation to continue the cycle.
Adding animals to the terrarium turns the container into a vivarium. Though many people refer to their reptiles' homes as terrariums, the truth is once the little guy is established, it's a vivarium. Of course, the vivarium needs to be appropriate for the creature taking up residence in it, so the focus of a vivarium is on the animals in the container. A terrarium is based on the plants it contains.
If you have an aqua-terrarium, you've designed a terrarium for plants that are semi-aquatic. If you've taken on semi-aquatic pets, such as some varieties of turtles and lizards, you're tending an aqua-vivarium. If you've heard of a paludarium, it usually refers to an aqua-terrarium or aqua-vivarium, although sometimes it means an established vivarium that depends almost entirely on its own beneficial bacteria and microfauna to maintain it. Though self-contained miniature ecosystems, terrariums and vivariums require maintenance to ensure they don't develop mold, rot or excess waste. Maintenance depends on what kind of plants or pets the container contains, as well as the size, depth of the substrate and other design elements.