Providing an engaging and safe environment is one of the top priorities when taking care of any exotic pet. Pet stores are notorious for sending new hobbyists home with small tanks and a couple fake plants, but these bare-bones setups are not ideal for an animal’s well being.

Bioactive enclosures mimic the natural environment from your pet’s native region, and they are self-cycling to reduce how much work you need to put in over the long term as an owner. If you want to make a bioactive enclosure for your exotic pet, there are just a few steps you’ll need to follow.

What Does Bioactive Mean?
The term “bioactive” has grown in popularity since the 1970s; if you’ve never heard of it before—or if you have, but you’re not sure what it means—you’re not alone. A bioactive enclosure is one that is made of living things, such as bugs and live plants, that create their own self-sustaining ecosystem. Rather than putting together an enclosure with some fake grass carpet and a couple plastic logs, owners who use bioactive enclosures recreate an animal’s native habitat inside their terrarium.

There are many advantages to approaching exotic care in this way. Your pet can enjoy a climate that is as close as possible to their home range, and animals can engage in their instinctual behaviors, such as burrowing, drinking water from leaves, or hiding among foliage. One of the biggest benefits is that bioactive enclosures are self-cleaning. While you’ll still need to do light spot cleaning from time to time and a substrate change once in a (long) while, most waste matter will disappear on its own to be incorporated back into the bioactive ecosystem. This is why most bioactive enclosures smell nice (like nature) and are simple to take care of once established.

The Pieces of a Bioactive Enclosure
If a bioactive enclosure sounds like a good fit for you, it’s simple to set one up! First, select the right enclosure size for your pet. Each animal will have its own unique needs, from terrestrial lizards that appreciate wide habitats with substantial floor space to arboreal snakes that need tall enclosures with lots of branches to climb. Once you choose an enclosure that’s ideal for the species you’re keeping, be sure to seal the joints with a material such as silicone caulk. This will prevent the natural moisture of a bioactive enclosure from seeping out from the enclosure’s seams.

Now that you have your base enclosure ready to go, you’ll need to add: Substrate The right substrate will depend on which species you’re keeping. Those from arid, dry climates often appreciate sand or loose topsoil, while inhabitants of humid regions may need sphagnum moss, coco coir, and more. Consider how well your substrate of choice aerates—that is, how easily it becomes tightly packed together. Aeration is crucial in a bioactive enclosure, because the soil needs to remain slightly loose to allow air, bugs, and moisture to penetrate.

Topsoil can easily become packed tightly, so consider mixing it with a textured addition such as coco coir or orchid bark. Many people see great success in creating a loose but robust substrate using a mixture of topsoil and washed play sand, which can be a useful blend for animals that want to create burrows that don’t collapse.

For some animals that don’t require substantial humidity, your work on the substrate might end here. However, those with greater moisture needs require an additional step.

Drainage Layer
For enclosures that will be frequently exposed to water through misting, raining, use of a water feature/pond, or fogging, incorporating a drainage layer is the next step in creating a bioactive enclosure. The drainage layer sits underneath the substrate and is made of pebbles and rocks, providing a place for excess water to go so that it does not stagnate in the soil. If your substrate is made of fine materials, you can use a screen to separate the drainage layer from the substrate to prevent mixing. Coarser substrate, such as bark and mulch, may not need a screen to naturally stay separate from the drainage layer.

Biodegradables
Once you’ve established how the floor of your enclosure will function (either with or without a drainage layer), you can build any necessary drainage and add your choice of substrate on top. Then, you’ll need to create a nutrient-rich environment to support all of the living organisms that will populate your enclosure. Biodegradables are items that will gradually break down into nutrients to feed your terrarium.

In nature, biodegradable material comes from everything from dead wood and plants to shed insect casings and feces. Your pet will take care of adding the poop, so focus instead on other natural items you can contribute, such as dead leaves and pieces of cork. Mixing these directly into the soil is akin to storing food for later; as they decay over time, they will replenish the nutrients in the substrate.

Organisms
Why bother with adding nutrient-rich material to a bioactive enclosure? Because this environment will support many forms of life beyond just your pet. Something needs to be there to eat your animal’s feces and clean up old shed, dead plants, and other natural parts of the ecosystem. This job, by and large, falls on insects. The two most common bugs used in bioactive enclosures are isopods and springtails. Most people know isopods as roly-poly bugs, and springtails are very small, white organisms that collect on moist surfaces. Both will consume organic material within the enclosure to keep it clean. Isopods come in many varieties that are suited for different climates, so do your research before selecting a breed. Zebra isopods are good for many low-humidity terrariums, while dairy cow isopods thrive best in enclosures with higher humidity. Exotic keepers don’t typically have to worry too much about which variety of springtails they get, and they’ll come in a container with some moist charcoal. You may dump this entire container, including the charcoal, into the enclosure—just be sure to provide the springtails a damp area to live. If your substrate is moist enough, adding worms is also beneficial to aerate the soil and keep the rest of the enclosure’s inhabitants happy. The worms, isopods, and springtails will gradually consume the decaying plant matter and cork, refreshing the substrate and eliminating waste.

Live Plants
Your natural bioactive environment is almost complete! The final living element to add is plants. Bioactive enclosures should utilize live plants wherever possible, because they perform an integral job in the closed ecosystem. Plants help to absorb excess moisture (including from the drainage layer), provide shelter for the bugs (often called a CUC, or clean-up crew), and produce clean, fresh air. However, many herps are curious animals, and they may sample whatever plants you place inside the enclosure. Thus, be very careful with the varieties you select. Bromeliads, pothos, hoya vine, and java moss are some common choices, but the best plants will depend on the type of animal you’re keeping in the enclosure.

Lighting and Heat
All of the living things you’ve incorporated into your enclosure will need light to survive and thrive. UV lighting provides the nutrients that plants need and signals when they should grow. The heat and UV requirements of your animal will vary based on species, but try to place UV and heat lamps near each other to facilitate vitamin D synthesis. They should be placed at one end of the bioactive enclosure so that there is a bright, warm side and a cool, shady, and moist side. For vertically oriented enclosures, the top will be the warm and bright area, while the enclosure floor serves as the moist, cool space.

Hardscapes
At this point, all you’ve got left is décor! Logs, branches, stones, and other decorations come last, once the ecosystem has been established.

Bioactive Challenges and How to Fix Them
Once established, bioactive enclosures don’t usually require much upkeep—that’s a big part of their appeal. Still, things can go wrong from time to time, especially for those new to creating these miniature ecosystems. Common problems include:

Over-Saturation
If your plants start to brown and die, or if you notice consistently soggy soil or pooling water, you have a problem with too much water. If you use a system to introduce moisture, such as a mister, decrease its spray duration/intensity or increase the delay between mistings. Over-saturation kills plants by drowning their roots and contributing to rot within the soil. This encourages the buildup of anaerobic bacteria, which outcompete the other beneficial bacteria and lead to a pH imbalance in the soil that may kill the clean-up crew and the rest of your plants.

Improper Substrate Mix
The substrate you choose is important, and it may take a few attempts to find the right mix. If your CUC or plants are regularly dying or not multiplying, it could be because your substrate is not suitable for them to thrive. Look for evidence that your isopods are molting; if you cannot find casings, you may need to add substrate elements that increase the moisture so they can properly shed. If they are simply dying and the plants are browning from the tips, your substrate may be too compacted, preventing the living organisms from reaching nutrition and water deeper in the soil. Add aerators, such as bark and earthworms.

Mold and Slime
In humid bioactive enclosures, mold and slime may begin to appear in especially moist, dark areas. This is a sign that there are not enough beneficial bugs in the enclosure. Springtails and isopods eat mold, and an enclosure that still faces a mold problem simply needs more mouths to contribute to the feast. Purchasing more CUC is beneficial not only to address the mold problem but to add some genetic variety to your colony for population purposes.