Exploring what makes a terrarium/vivarium " bioactive" and how to do this with your own.
Recently, there is a growing trend towards "bioactive" terrariums and viviariums. The concept is simple enough on its face but when I have conversations with people about the subject there seems to be a little confusion or misinformation regarding some aspects. This post will explore the components of a successful bioactive terrarium, why success isn't always achieved, and other related aspects to this topic.
As mentioned, a bioactive terrarium (or vivarium as it would technically be defined) is one in which an enclosed space, usually a glass tank, is used to house one or more species of terrestrial animal, along with plants, mesofauna, and microorganisms. The mesofauna and microorganisms help break down the waste products of the primary species, which both reduces the frequency of maintenance required and also provides valuable nutrients for the plants. When done correctly the result is a "self-sustaining" living space that is healthier for all the inhabitants and means less frequent upkeep for the owner. They can be a challenge to properly setup, but once they are established bioactive enclosures are easier to maintain and the best way to keep captive herptiles and invertebrates.
Do you need plants for a tank to be considered bioactive?
While generally speaking plants are usually considered an important component of a bioactive terrarium, however it isn't strictly necessary to have living plants present make your setup bioactive.
Even the best keeper of reptiles, amphibians, or invertebrates can struggle with keeping plants alive in a terrarium. They are so much more than just living decorations and it may be more useful to think of them as roommates to your animal(s) with their own needs in addition to those of whatever critter you're maintaining. Plants are key components to cycling nitrogen, carbon, and water cycles; they help prevent the buildup of nitrogen which can be toxic at high concentrations. They also convert carbon dioxide into oxygen for the tanks inhabitants. The flora in a tank help maintain appropriate humidity levels and help create microhabitats within your terrarium.
Lighting and water are probably the two major factors when it comes to healthy plants in the terrarium. For light, it is hard (but not impossible) to give plants too much light. Even modern grow lights can only match a fraction of the UV output of sunlight, and good choices for plants for terrariums often are tied to their shade tolerance because of that. The amount of water needed is largely tied to the type of biome you are trying to recreate and species selection is important here - some plants need quick draining substrate that keeps their feet dry, while other species don't mind, or even do better, when their feet are wet.
To keep this post a reasonable length I won't delve into the details and aspects of plant care for your terrarium since that is a topic large enough for several blogs. What I will say is make sure the plants you have in your terrarium are a compatible fit for the space you have them in, for the animal you have them paired with, and for the biome which you are attempting to replicate. If you chose a large or fast growing species be aware that it may require a lot of pruning to keep it the desired size. Should you have a omnivorous or herbivorous species it is important to chose nontoxic plant species, or a way of creating a barrier so that the plant isn't denuded by hungry inhabitants. For a desert or arid biome it doesn't make a lot of sense to use tropical rainforest plants, and vice versa, since the conditions you're aiming to replicate within the enclosure simply won't match those required by the plants (mainly water and light requirements). The key here is research, research, research!
Now, the stars of the bioactive setup, the keystone which holds it all together...*drum roll*....mesofauna! Which is just a fancy term for springtails and isopods and other small invertebrates which play a vital role in nutrient cycling and breaking down waste. These are the clean-up crew (CUC), the tank "janitors," that break down feces and mold and unlock nutrients to a form usable to plants (along with the microorganisms present in the substrate). Does your setup require isopods and springtails? Isopods, while highly desirable, aren't 100% necessary for a bioactive setup. Springtails on the other hand are vital component to a bioactive terrarium and without them you are missing a essential link. Isopods are shredders of course material, breaking down dead leaves and droppings into fine material. This fine material is what the springtails feed upon which they further breakdown into usable material for plants. They also eat mold, a irreplaceable role since the high humidity and low airflow of a terrarium create the perfect conditions for mold to flourish.
Both isopods and springtails require moisture to survive. How much is dependent on the species, with some isopods being surprisingly drought tolerant. When it comes to springtails they are less forgiving of arid conditions, although some species are still quite tolerant. When it comes to drought tolerant pods and springtails, even those which can handle drier conditions need a place in the terrarium where they can 'recharge,' ie a spot which offers a little moisture. It is useful to have a couple pieces of bark or dead leaves to help create this recovery corner for your CUC. This is where it is useful to have live plants in your setup, since in their root network the little pockets of moisture are easier to find and help create the microhabitats sought by springtails and isopods.
It is possible for other mesofauna to take the place of isopods if they perform similar tasks and fill the role of course shredder. One which readily comes to mind are lesser mealworms. This species is very adaptable and much more drought tolerant than any isopod species I've worked with. They work quickly to break down organic waste and leftover food, and are also make excellent feeders as well.
When it comes to breaking material down further, springtails are difficult to beat. One of the few alternatives I have found are oribatid mites, also called 'moss mites.' Such an important role these mites play in breaking down fine materials that some researchers believe they are one of the primary builders of soil on this planet and as a group play an outsized role in the creation of the thin organic layer that this entire planet relies on for food, directly or indirectly. Regardless of the degree to which they build our soils, two of the other features I like about moss mites is they don't breed all that quickly (for mites) and also that they create competition for grain mites, making the latter less likely to establish. I'll be going over mites as a topic in more detail in a future post coming up soon - that's another topic which requires a dedicated post of its own just to do an overview given the amount of material to cover.
I think I will end things here for now and likely do a follow-up part 2 to this, but I feel the basics have been covered;
While plants greatly benefit and are important aspects to a bioactive tank they aren't absolutely necessary to make your setup bioactive.
Mesofauna are crucial to creating a bioactive tank since they help break down waste matter. Isopods and springtails are the most commonly used combo.
Levels of moisture can vary in a bioactive setup but it is important to at least provide a moist refuge for your mesofauna for their survival.
While springtails and isopods are the most commonly used combo to help make an enclosure bioactive they aren't the only invertebrates which can be used.
Thank you to all the readers of this post. If you have any questions regarding any aspect of bioactive enclosures please don't hesitate to add a comment below and I will answer as soon as possible. If you'd like to purchase some inverts to help make your setup bioactive please visit our SHOP. Cheers!