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

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. Most plants have different requirements, so I suggest researching everything thoroughly before you put it in the enclosure. You also don’t want to find out that it is toxic to an animal that is herbivorous.

Birds Nest Fern - a fern native to Australia. They do well in bio active enclosures, but can get quite big.

The final layer/finishing touches

The top layer/finishing touches serve two purposes. They are aesthetically pleasing, and complete the naturalist look, but more importantly for effectiveness in your bioactive enclosure. They give the clean-up crew places to shelter and conceal themselves from your reptiles/amphibians and do their job. Natural finishes as opposed to commercial hides are strongly recommended. For long-term durability choose logs that are rot resistant. If you choose an already rotting hide you will have to replace it. There are quite a few places that recommend Mopani and the store-bought woods. I have found these develop mould over time in enclosures. If you have a water feature, they leak tannins terribly. They look fantastic but aren’t overly practical for long term use. Cork Bark is a popular choice – buy it from a nursery that specialises in orchids, it will be cheaper than a pet shop. A sturdy rock is great for not only warmth but something to rub against if sloughing issues are present. Wash woods or rocks before adding or make certain no pesticides have been used if you are taking from your yard. Pinecones, dried seed pods etc can also be used. As these break down over time, they go from valuable hiding places to food for your clean up crew. I would like to add if your bioactive enclosure is for venomous species, minimizing risk is the desired outcome. I would recommend minimum amount of objects obstructing view, or that need to be removed from the enclosure every time you need to find the occupant. Moss is one way of covering the substrate layer. It looks very nice, but not always natural depending on species living in the enclosure and plants chosen. It’s also inexpensive as almost everyone has access to moss in their garden. A lot of people don’t use moss as a complete cover as they struggle to keep it alive. (I’m one that struggles to keep it alive!) Leaf litter not only looks natural it is beneficial – it provides a naturalistic cover for both the clean up crew and your pet (this can make a world of difference to a shy or nervous inhabitant), but it will also provide hummus over time and provide food for the enclosure’s microfauna. Your leaf litter will need to be topped up over time. When you need to re add will depend on the type of leaves that were used, the humidity of the enclosure, the size of the clean up crew and the animal(s) kept in your bio active tank. If you are looking for the most realistic bio active set up you can achieve, a mixture of moss, creeping plants and leaf litter can be used.


Correct lighting for your bio active enclosure is a is a must. Lighting is not there purely to light the enclosure to make it easier to see in, it should provide heat, UV and light. Everything in your bio active enclosure will need this to thrive. If adequate lighting is not supplied the plants will not acquire the energy, they need to replace cells that are dying, dead or damaged, nor will they grow properly. Your inhabitants will also need heat (species dependant) and will benefit from UV.

Our lighting system is the Exo Terra lighting that goes with the enclosure. The lights are Exo Terra Natural Light Full Spectrum Daylight Bulbs. We have UV lighting behind the Exo Terra light casing pictured at the front with Exo Terra Reptile UVB 100 (Repti Glo 5.0 Compact Fluorescent). It warms the enclosure to 26 degrees.

Clean Up Crew.

The insects you add to your bioactive enclosure will not only eat the waste, left-over food scraps, etc they will also in some cases help to aerate the substrate and keep it healthy. Depending on the enclosure inhabitants, they can provide a tasty meal if they are caught. The biggest advantage of having a decent clean up crew is the enclosure’s substrate will be kept free of mould, bad bacteria and the nasty odours that arise from these problems.

· The most used insects in the clean-up crew are:

· Isopods (Woodlice, Pill bugs etc)

· springtails

· earthworms

· millipedes

· beetles

When your ecosystem is in place in your bioactive enclosure and your clean up crew have adjusted to their new habitat and are thriving and breeding, you won’t have to do too much in your enclosure other than spot cleaning. Leave any decomposing matter such as wood and leaves, as they will be utilized for food by the clean-up crew. Until you see them thriving it is a good idea to add a bit of extra food for them to thrive. The cheapest way of doing this is by burying vegetable peelings in the substrate weekly. Once you see the colonies expanding you should be able to stop doing this.

Isopods (also commonly referred to as pill bugs or rolly pollies) are fantastic little cleaners. Isopods are not bugs; they are crustaceans. They possess gills - this makes it possible for them to exist in environments that are moist and have high humidity levels. If Isopods are part of your clean-up crew, your substrate must be kept moist for their survival as well as the flora’s. You’ll regularly see them under bark, logs, water bowls and in your leaf litter. Not only will they consume the waste produced in your bioactive enclosure, but they will also aerate your substrate and scatter nutrients right through the substrate as they go about their business, and when they defecate, it will fertilise your plants. They are also cool to watch!

Springtails are amazing little creatures that measure in at approx. 6mm. They are one of the most common members of the clean-up crew. Most bioactive enclosures are tropical, and Springtails will flourish and breed well in these conditions. They devour any mould or decaying matter in their terrain. Earthworms are used for their ability to aerate the substrate in the enclosure. Whilst they move around in the substrate, they will move the organic matter around as well. Over time this helps keep the bad bacteria and mould at bay. Like the other insects in the clean up crew their waste is an invaluable fertiliser. Worm castings comprise of the essential nutrients’ plants need to thrive and they also improve the soil.


It’s not uncommon to see fungi pop up from time to time in your bioactive enclosure. This is normal and not a bad thing. This is the maturing bodies of the fungi system in the dirt. This is made up of a fine, white, infrastructure known as mycelium. Studies have shown this is beneficial for plant growth. Fungi grown in parallelism with plants helps the plants grow and aids in nutrition and will speed up the bio active cycle.

A Final Note –

A bioactive enclosure consists of several essential elements that merge to produce a naturalistic, visually enjoyable enclosures for both reptiles and amphibians. It takes more than just live plants to make it bioactive. The clean-up crew are a vital part of a bioactive enclosure, just as the correct substrate is. The living flora provide clean air, maintain humidity levels, and offer shelter, enrichment, and food (species dependant) cover for inhabitants. A correct substrate mixture will allow the plants to take root, grow and flourish. The microfauna clean-up crew will eat animal waste, leftover food and mould. It is then transformed into a product that is more adequately processed by any flora (plants and fungi) in your enclosure. An enclosure just containing live plants (whether planted in the ground or in pots) is not classed as a bioactive enclosure.

A naturalistic enclosure is an enclosure containing synthetic materials – hides, plants, fake grass, etc to mimic the appearance of a natural habitat. Plenty of products are available commercially that look realistic. These must be cleaned regularly. A naturalistic enclosure is easier and cheaper to set up than a bioactive enclosure but doesn’t look quite as good as the real thing.

After much discussion we ended up deciding that this enclosure was for a Common Death Adder (Acanthophis antarcticus) so we went for minimalistic plants and hides. This is the enclosure a couple of months in. There is a native orchid (I lost the tag so I cannot help you with its name, but it was bought at the nursery mentioned below) at the front right, a Birds Nest fern at the back which has quadrupled in size, another native fern in the middle, (here is where I admit I suck terribly at remembering plants' names), a Carbeen tree (I may of misplaced that tag too, but Scott tells me its definitely a Carbeen Tree) in the left hand corner who has come good since that photo and the grass at the front which goes through stages of thriving, being dormant, dying off and being trampled by the Death Adder. Its a continual tuft of grass.

In a future blog we will share with you our paludarium and step by step instructions for doing one yourself.

Resources and recommended reading:

Courteney-Smith J. 2016, The Arcadia Guide to Bio-Activity and the Theory of Wild Re-Creation, Arcadia Products PLC, United States

https://www.peteshobbynursery.com.au/ - awesome nursery for native plants

https://fameorchids.com/index.php - great place for Orchid bark.

We have no affiliation with Exo Terra. I use and recommend their products because I like them - their durability and practicality and find them to be incredibly long lasting. We have enclosures, furnishings and various products from Exo Terra that are 20 odd years old and are still in perfect working order. I also quite like the way they give back to the reptile community and the research they put into their products.

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