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Bioactive enclosures.... Are they right for you?

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Bioactive Enclosures are often referred to as “no maintenance enclosures”. This is not the case, no enclosure is completely without maintenance. You care for a living animal and there will always been some form of care and attention needed to both the animal and its enclosure/living space. The animal you choose to put in the enclosure will also determine the amount of maintenance needed in a bioactive enclosure. E.g. frogs will not produce as much waste as a larger animal. The clean up crew will have a much better chance of coping with the waste of a couple of frogs or small lizards than say a medium-large snake. Not only will a large snake demolish any delicate flora planted, but they will also need most of their waste removed as it will simply be to much for the clean up crew to deal with. When planning your bioactive enclosure, think about what animal will go in there first before planning on what to plant, and what to use as your substrate and clean-up crew.

After removing the packaging, we gave the empty enclosure a thorough clean out with a watered-down mixture of F10 and water. We then washed this out with water and waited a week to thoroughly air out the enclosure before adding anything to it. This is probably over precaution, but as we weren’t entirely sure at that stage what we were putting in the enclosure (e.g., frogs absorb through their skin), we wanted to be safe than sorry. Our enclosure is an Exo Terra Natural Terrarium Large/Tall, which measures 900L x 450W x 600H.


The background is the first thing to go in as you cannot add it later without uprooting the whole tank. You can buy a commercially made one, get someone to make one, make one yourself if you have the time and the skill or leave the back wall blank. Most enclosures these days have a feature back wall as part of the buy. All have their benefits. The back wall is not only easier on the eye, but it gives the inhabitants extra space to move about if they climb. It also gives you more surface area for plants. A clear back wall is a lot easier to clean….

We choose to leave in the backing that came with the Exo Terra enclosure. It has a nice rocky look to it, and we were still “discussing” inhabitants.

Layer 1: The Drainage Layer

The first layer to be installed is the drainage layer. This is often referred to as a false bottom. The drainage layer is there to catch any water that wells through the substrate. This prevents stagnation, bad bacteria from forming and the bad smells that will arise from the stagnation and bad bacteria. Drainage also obviously prevents the substrate layer from becoming sodden. An overwatered, stagnate enclosure can result in bad health for your flora, microfauna, and animals. On top of this, the drainage layer plays a vital job in allowing the plant root system to grow. Give your bioactive enclosure the right components and it all goes into helping to sustain a healthy microfauna population and will keep the humidity stable inside the enclosure. The drainage layer should be 2-3 inches in height. This is dependent on the size of the enclosure that has been used. The drainage layer should never be left to thoroughly dry out as this will have an impact on the humidity levels in the enclosure. The drainage layer can be made from a few different mediums – hydro balls/clay balls, lava rock, gravel and plastic eggcrate also known as light-diffuser. You can combine these mediums or stick with one.

Clay balls/hydro balls are utilized across many fields. As the name suggests these small pebbles/balls (depending on the product) are made from clay. Clay is lightweight, especially when using it in a larger area, when compared to lava rock or gravel. Being absorbent, they have a high porous space which allows good bacteria to amplify, are a good colonization for microbial populations, are environmentally friendly and reusable. They absorb water and then release it through evaporation. This will provide increased humidity in the terrarium.

When using gravel, think about the weight and placement of the tank. It is the cheapest option, but also the heaviest and poorest in terms of functionality. Gravel won’t deliver on the capillary action that the plants need to thrive like the other methods of drainage will.

Plastic egg crate is panels of plastic in the configuration of a square lattice. It’s easy to work with – both cutting and in construction of whatever form you desire it. It can also be used to produce a false floor that will hold the substrate above water. Usually plastic egg crate/light diffuser is used in setups that include large volumes of water, such as paludariums or ponds. You can also creating spaces to hide filters or pumps preventing from ruining an aesthetically pleasing view.

We used Bio Drain from Exo Terra. Bio Drain is essentially lava rock. Lava Rock is a natural, porous, non-decomposable substrate that allows excellent drainage in the bottom of a terrarium. It will not rot or decompose.

Whatever you choose to use for the drainage layer, it should be thoroughly washed before putting in the enclosure. Washing removes excess dust, dirt and anything else that it may of come into contact with.

The obvious way is in a colander like we did, running water over the rocks and mixing around till the water runs clean. This is one of the upsides to both of us keeping – you don’t have to sneak the stuff out of the kitchen to use in the herp room. (Although I did put my foot down in no uncertain terms after someone “over defrosted” pinkies in the microwave.)

There is a quicker way to do this – dump the whole lot on a dog bed and hose down till the water runs clean. But as you can see, Jazzy wasn’t overly willing to help out…

The washed drainage layer in our bioactive enclosure. We used 4 x 2kg (4.4lb) bags to fill the enclosure.

We didn’t add a drainage system. If you choose to add a drainage system now would be when you add one.

Layer 2: Drainage Mesh

The next step in making a bioactive enclosure is placing a barrier between the substrate and the drainage layer. This is referred to as drainage mesh or a drainage screen. The role the drainage mesh plays is to stop the substrate from dropping in the drainage layer while allowing air and water to flow through. The substrate layer falling into the drainage layer can obstruct the space needed in the drainage layer. (see drainage layer for problems if not done properly) Suitable mesh to use for this layer can be any non-toxic, thin material that won’t rust. Weed mesh, plastic mesh and fish netting are commonly used. If springtails are part of your clean-up crew, make sure they are able to travel through whatever drainage mesh you decide to use. Admittance to the drainage layer will give you better reproduction. No matter which product you choose to use, the whole drainage layer MUST be covered.

We used Bio Drain by Exo Terra. It’s non toxic and non degradable.

Layer Three: Substrate Layer

Next comes the substrate layer. The substrate layer will depend on two factors – the flora and fauna you wish to keep in your bioactive enclosure. An appropriate substrate should be able to not only maintain plant life, but it should also be able to keep alive the microfauna, as well as of the roaming inhabitants. Improper substrate choice is one of the most common mistakes made by people first starting out with bioactive enclosures. One product alone is not a suitable substrate if you are wanting a long-term bioactive enclosure. One medium will become dense and break down. (Think of a plant in a pot that has been there long term – have you noticed how the potting mix shrinks in size and when this happens the plant doesn’t look as healthy as it once did) Once this happens the substrate will not be able to maintain the microfauna population. This can result in a detrimental anaerobic soil condition. You will want at least a good 10cms of substrate if you can fit it in your enclosure. This allows plenty of room for root growth which will lead to plant growth, the clean up crew to find their own homes, and decent drainage and air flow.

Buying a premade substrate.

If you buy a commercially available substrate, research who you are buying from and put the money into a quality product. If you buy the cheapest one you see with no research into your substrate or your plant’s needs you can end up killing at best just your plants, at worst your plants and ALL inhabitants of your bioactive set up.

Mixing your own substrate.

An incorrect selection of substrate is the biggest recurring misjudgement made by novices. Research your needs firstly of your animal, then the habitat and then the habitat’s fauna and needs. A single medium will not give you long term success in terms of substrate. The most commonly used ingredients for mixing up your substrate blend are:

· organic soil

· sand

· coconut fibre, (cocoa peat)

· wood bark

· moss

· activated carbon/charcoal

· potting mix

· orchid bark

· rotting leaf matter

· sphagnum moss

Organic soilOrganic soil is soil that is made by the decomposition of plant and animal objects to produce a mini-ecosystem that is plentiful with nutrients and minerals with microorganisms that feed and breathe life back into the soil. Simply put, organic soil is how soil is in nature without humans adding chemicals to it. Sand – Sand is prominently used in drier/arid enclosures. Sand should also be added to other mixes to improve soil quality. Sand mixed through your substrate will add air space and help with drainage. Use a coarse grade rather than fine grade sand. Coconut fibre – Coconut fibre/Coco peat is used to improve soil drainage and help retain moisture. Coconut fibre is slow to break down and rot resistant and causes air pockets in the substrate mix that will permit any surplus moisture to escape away from the plant’s roots. Wood barkBark will stop the substrate mix from sinking when it has been watered. Bark chips will trap air and water which will be utilized by both your plants and your clean-up crew. Moss – Moss is used for moisture retention and is great in bio active setups that require high humidity. Activated Carbon/Charcoal – Activated carbon is mixed through to not only help with drainage in the substrate mix, but also eliminates any odour that can arrive from any bacteria, fungus, or rot in the bioactive substrate. Potting mix – If using potting mix in your bio active substrate a high-quality potting mix should be used and in sparing amounts. It is imperative that you check that the potting mix is both fertilizer free and pesticide free. If you have access to organic soil, it is a much better option. Orchid bark – Orchid bark is bigger than wood bark chips. It is also more expensive. Rotting leaf matter – Decaying leaves produce what is referred to as “humus”. Tree roots constantly bring up the mineral salts from the earth. Amounts of these precious salts remain in the leaves when they fall to the ground. To put simply, humus is a slow-release, natural fertilizer for your plants. Hummus also brings aggregation. Aggregation is what produces a loose soil, which in turn improves the soil structure. This makes it easier for the plants roots to grow and thrive as they have been given access to water, nutrients, and oxygen. Sphagnum moss - Sphagnum Moss is used for its ability to retain water. Some people use it to replace moss as a “carpet” across the top of the substrate, some people don’t like the look of that and use it mixed in the substrate. If you coat the top layer with Sphagnum moss, it will help to keep the occupants of the enclosure away from the substrate, which helps keep them looking neat and tidy. It is important to keep in mind though, a large number of plants will not grow well in sphagnum moss. Sphagnum moss will break down quicker than your substrate will. This can have the negative effect of restricting the airflow through the layers. If you are wanting to use Sphagnum moss in your bio active enclosure on the top, use it sparingly – no more than a centimetre on top.

We went with a premixed substrate. We’d heard nothing but glowing reviews on the substrate mixes AK Reptiles produce so we used that company. We were doing a tropical enclosure so we got the Temperate mix. Cannot recommend it highly enough if anyone is needing substrate for their next bio active enclosure. The link to their Facebook page is at the bottom of the blog with the recommended reading. The customer service is as great as the product itself and months later our bio active enclosure is still thriving. They specialise in custom backgrounds as well. They look fantastic and we will be using them in future projects.


Your choice in plants is entirely up to you. It will depend on enclosure size, the husbandry requirements for the enclosure inhabitants, if you are happy with any plants that you find aesthetically pleasing or want plants from specifically from the area your animal inhabits naturally. If it is your first time and you are not overly confident in your green thumb, my suggestion would be to get plants that are a bit harder to kill, not necessarily ferns found in the area local to your animal(s). It may not be exactly what you want, but it will greatly increase your confidence to the step of harder to maintain plants.