What is a Bioactive Terrarium? (+ How to Make One)

Turning your terrarium bioactive is effectively a levelling-up of your ecosystem. Bugs, fungi and knowledge are the three key tools to taking your biome a step further.

In this article I’ll tell you exactly how to make a bioactive terrarium and explain the benefits you can reap from doing so.  

I’ve added years of life onto my own terrariums this way; many that were showing signs of an unhealthy bacteria build up have now bounced back and rooted themselves into the realms of the truly self-sustaining.

Let’s get into it.

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The ultimate end goal for many terrarium creators is to make something as self-sustaining as possible. There’s a great satisfaction in having created a real ecosystem that operates on a cyclical basis. Adding in elements to promote bioactivity is a magnificent way to achieve this.

We’ll be talking a LOT about microfauna. These are little terrarium bugs often referred to as the ‘clean-up crew’ (or CUC for short). I’ve recently also heard the term tank janitors, which is adorable, and I’ve decided to coin my own term: custodial critters.

If you’re a bit grossed out by bugs, the combination of their skillset and adorable nicknames are sure to ease your distaste.

In short, a bioactive terrarium will tend to be healthier and live longer – as well as retain certain abilities such as combating detrimental bacteria.

Let’s first run through everything you’ll need to create a bioactive terrarium from scratch inside your chosen glass container. For the moment we are specifically referring to closed, tropical terrariums.

• Drainage. Find yourself some gravel, sand or Leca for your base layer. A false bottom allows excess water to ‘pool’ without soaking your substrate and thus rotting your roots.

• Activated charcoal. This material has an exceptionally high surface area making it an excellent absorber of harmful chemicals and bacteria and subsequently a perfect feeding ground for your microfauna.

• Substrate. The substrate layer is the heart of your terrarium. As well as nutrition and space for root growth it will allow your bugs to reproduce. In addition, it will be the centre for essential fungal development.

DIY Bioactive Substrate

Your bioactive substrate mix will depend on your plants, though generally it is likely to combine orchid bark, peat moss, tree fern fibre and often coco fibre. You can, if you like, include activated charcoal in your substrate mix rather than as a separate layer.

This mix will allow for aeration, water retention and nutrition. A high organic content is crucial for long term sustainability.

Any version of the classic ABG mix is a good place to start.

👉 Shop ABG Mix on Etsy.

Up until now it’s been looking business as usual, so let’s get into the good stuff.

1. Microfauna. First and foremost, your custodial critters will serve as the MVPs of your bioactive ecosystem. You have a lot of options when it comes to selecting your staff and we’ll outline the best of them below.

As detritivores, their primary function is to break down organic matter and convert it into nutrients for your terrarium plants. Some bugs have secondary characteristics that bring additional benefits.

2. Fungi. Mushrooms and mycelial growth often get a bad rap within the terrarium niche, though they famously play a pivotal role in the natural world. Like microfauna they decompose waste material incredibly efficiently and return goodness in its stead.

In turn, plants use these nutrients to grow, produce oxygen and encourage humidity within the ecosystem. 

Many soils, plants and woods will contain beneficial fungi spores ready to develop mycelium.

3. Natural decoration. Certain woods you can use are naturally more resistant to rot, such as mopani. Over a long period of time woods will break down and can become a further source of nutrition for your microfauna.

Alternatively, if you’d prefer to achieve a more mountainous look – go for lava rock: it’s so porous that it can aid in water retention and allow for the creation of gorgeous natural structures.

This element is usually best added after your substrate layer and before your plants.

4. Leaf litter. There’s a plethora of different bioactive feeds for your clean-up crew out on the market right now. But a more natural solution is to sprinkle your terrarium enclosure with a little layer of leaf litter upon creation. It’s the perfect starter source for your bugs’ nutrition. 

You can take leaves from the wild, but make sure to microwave them first – so that any dangerous bacteria are removed.

If it’s not yet fall season, or if you don’t fancy microwaving your back garden you can grab a bag on Etsy.

Adding your dry leaves is your final step to turn your terrarium bioactive!

Although the functions performed are often similar, there are different bugs for different occasions.

Take a look.

Springtails

Springtails are arguably the most popular option when considering what custodial critters to bring into the fold.

These detritivores are famed for their ability to consume and remove mould (or, mold) and are small enough to be an appropriate option for almost any sized terrarium.

They’re cheap and easy to get your hands on, and infrequent feeding is enough to keep their colonies sustained.

Though usually light white or tan, they do come in a range of colours.

An added bonus is their ability to jump incredible heights using their tails (hence the name). It’s not relevant, but no other insects on this list can do that. So, 1-0 to the springtails.

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Worms

Worms are another great choice.

They are not always an appropriate option given their size, though in a medium-large scale terrarium worms perform not only the typical duties of breaking down organic matter but also aerate the soil via tunnelling – which is incredibly beneficial over time, as otherwise soils tend to compact.

As well as earthworms, mealworms are another common option that are readily available online.

Isopods

Isopods (aka pill bugs) come in many sizes often adorn striking visuals.

Their different colours and often quite adorable designs (check out the extremely cute Rubber Ducky Isopods). A growing fascination in these critters has spawned a dedicated hobbyist culture, and I can see why!

If you’re less partial to having large bugs roaming your ecosystem, there are cultures of dwarf isopods that are equally efficient eaters of organic waste.

Isopods and springtails also make excellent partners in a cleanup crew, as they work together synergistically.

> See Isopods from specialist breeders at rubberduckyisopods.com (they sell some extremely pretty and unique types of isopods).

Millipedes and Centipedes

Millipedes are known consumers of undesirables and are another safe option for keeping your terrarium bioactive. Much like worms, their long bodies can help to aerate your substrate.

Centipedes are a less common choice for terrarium enthusiasts. Though, as predators, they can fulfil the role of population control.

Isopods and springtails breed readily, so if the right balance can be struck you could create a true equilibrium.   

Low maintenance is often the sell for terrarium enthusiasts. Bioactive terrariums, if done correctly, can reduce your responsibility even further. Though, it’s never a guarantee you’ll completely forego any duties.

Humidity and Water Levels

The plants, moss and microfauna inside your closed terrarium all prefer a humid environment. If you’ve set up your terrarium correctly (we’re talking moist, well-drained soil) and misted appropriately; you will rarely need to adjust the humidity level.

It may be the case, however, that your terrarium isn’t completely sealed or that it hadn’t received a decent moistening from the start.

Fortunately for you, there’s a LOT of ways to tell if you’re terrarium is a little on the dry side:

• Is your soil dry to the touch?
• Are your plants drooping or turning brown at the tips?
• Is your moss looking crispy and lost its fluff?
• Is there a total lack of condensation on the glass?

If you answered ‘yes’ to any or all the above, you may need to top up your tank with a little bit of the good stuff.

If the soil itself has gone dry and your drainage layer is looking arid, gently (and I mean gently) pour some water at the base of your plants and let it spread across the substrate.

Remember, you want the soil to be moist but still able to drain.

If your soil is damp but your plants and or moss are a little crispy, or you’ve seen no condensation for weeks, grab your mister and evenly coat your flora. Your bugs will thank you, too.

Trimming Plants

This one is a matter of taste.

Some like to just let their terrariums go wild (I tend to be one of those people) while others prefer an occasional pruning to help balance the design of their ecosystem and keep one plant from dominating the rest.

Pruning is a simple task. Take a pair of scissors (long, aquarium-scaping scissors are the best) and carefully aim the snippers above the node and take off any unwanted excess.

What’s a node, you ask? The base of the branch, bud, or leaf are attached to nodes – so just above where your plant has leaves. This will help stimulate new growth.  

Feeding

Your microfauna colonies will naturally grow and shrink depending on the abundance or food available. This is as in nature and perfectly healthy for your custodians.

Though, if it appears your colonies are shrinking to a dangerous extent – don’t panic! You can always top them up with some additional food. Leaf litter will do the trick, or even a sprinkling of dry active yeast can be a great food source for these critters, if you have it to hand.

Some food and a little bit of lovin’ is all they need to get back on track.

Cleaning Your Glass

Over time you can experience a build-up of algae on your glassware.

This is most commonly due to overexposure to light in combination with high humidity.  

Although algae aren’t necessarily detrimental to your ecosphere, it may not be the look you were after. I’m actually quite enjoying the slow build-up of algae on some of my older terrariums, it shows their age!

But it’s not for everyone. And fortunately for those people, the solution couldn’t be simpler. A little bit of kitchen roll on the end of some tweezers is all you’ll need. Gently rub the affected areas and voila, algae avast!  

Actually, yes!

Bioactivity tends to be synonymous with the closed, tropical-type terrariums. Though, your arid planter can be brought to life with all the benefits and beauty of the former.

For more advice on this, you can read my article on creating a desert terrarium though, there are a few things to note if you want to go bioactive.

Avoiding a Break-Out

As your containers are open there’s some opportunity for your microfauna to escape. Now, if you’ve set things up correctly they shouldn’t have an incentive to do so, but it’s imperative that you take steps to ensure this can’t happen.

The safest option is to only consider a bioactive arid setup inside of a vivarium tank, whereby the container is still essentially sealed with ventilation holes and / or fans to regulate humidity. It’s technically more of a bioactive enclosure than a terrarium – but who’s keeping score?

You don’t want your bug buddies to meet an early and unexpected fate, nor do you want to introduce an enclave of giant isopods to your local play park.

Bring in the Dry Guys

Arid set-ups are hostile environments to our usual moisture-loving clean-up compadres. You’ll need to instead choose some creatures that come from a natural environment closer resembling the desert.

Some great, affordable options:

• Mealworms
• Arid Springtails
• Blue powder isopods

And remember, as your desert terrarium is likely to contain less organic material you will need to top it up more frequently with some tasty edibles, such as leaf litter.

So, there we have it. A comprehensive guide to the bioactive terrarium. Now it’s over to you to give it a try.

Tell me, which microfauna do you think you’ll try out, or are there any I’ve missed that you’re particularly fond of? Leave a comment below. 

Next up, check out our How to Make a Terrarium (Beginner’s DIY Guide).