Transforming an old aquarium into a vivarium suitable for a reptile, land-dwelling amphibian or invertebrate saves you the cost of a new tank. It also does not matter if the old aquarium had a leak. The procedure and materials vary depending on which species you plan to keep as a pet. The more closely the vivarium mimics its natural habitat, the more content and healthier the animal will be. For this reason, research the specific needs of your pet carefully beforehand. Most lizards, tarantulas and toads and other small, terrestrial animals need much the same type of basic set-up, but the exact habitat required varies.
Drain any remaining water out of the aquarium. Dispose of the aquatic plants, whether alive or dead, in the garbage or place on your compost heap.
Place the gravel and rocks into a bucket with hot water. If you plan to reuse the gravel or rocks in the vivarium, they must be sterilised to kill any parasites or pathogens that might infect your new pets. Add ½-cup household bleach per gallon of water. Leave for 24 hours, rinse thoroughly and leave to dry. Alternatively, boil them in a pot on the stove for at least 30 minutes.
Create another bleach solution of the same strength in a bucket and wipe down the tank with it. Otherwise, use a reptile-safe disinfectant per the instructions. Rinse the tank thoroughly. Rinsing the tank in a bathroom tub or outside makes the task easier. Dry with paper towels.
Add a layer of a suitable substrate to the tank. Depending on the animal you wish to keep, this could be chemical-free potting compost, paper towels or bark chippings from a reptile supply store.
Position a reptile heat mat under one end of the tank if required.
Place rocks, branches or large pieces of bark in the tank to provide hiding and climbing places. Some animals also like growing plants, such as grasses. Check if the plant is suitable for the animal.
Add a shallow ceramic dish with water, if the animal needs one. A dish with roughly textured, sloping sides makes it easy for small animals to access their water.
Mist the tank to raise the humidity, if necessary.