Bioactive terrariums are the most authentic and natural manner of reptile keeping, and consist of all of the pieces of a fully functioning natural ecosystem. These pieces consist of proper, naturalistic substrate, live plants, and a dedicated cleanup crew of isopods and springtails to nitrify the soil.
Cleanup Crew
The most important element of a bioactive terrarium, the cleanup crew enriches and aerates the soil, and cleans up animal refuse. The most common genuses of isopods utilized for this purpose are armadillidium, porcellio, porcellionides, & trichorhina.
Some work better for different humidity levels, and even more so on a species-specific level, and choosing the right 'pods depends on the reptile they'll be cohabitated with. Note that any member of a cleanup crew will be 100% committed to eating protein, as such found in
fish food or shrimp pellets, but more importantly, leaf litter and decaying organic matter, including animal waste. All species should also have ~4 or more inches of substrate to allow for adequate burrowing and molting, and should have 24/7 access to a calcium source. As a
general overview of more specific species, we'll cover a few and their properties:
Springtails
Coming in several varieties and colors, springtails are found in virtually every environment in the world. These small invertibrates jump with a small body part called a forcula, and decompose decaying matter that would otherwise grow mold, decreasing the chances of a spore
outbreak. These also tackle animal waste and break down ammonia, helping cycle bioactive terrariums.
Armadillidium
One of the more common genuses of isopods worldwide, with the domestic species armadillidium vulgare able to be found in your own backyard here in Ohio, and their respective subspecies, are excellent tank cleaners, or even display isopods. These usually have
short, chunky bodies, and thick antennae protruding from beneath their shell. Some common morphs include a. maculatum, or zebra isopods, a. klugii, or clown isopods, and a. vulgare 'magic potions' which are more displayable. Their mild reproduction,
consumption, and low speed make them manageable and simple to care for for the most part.
Armadillidium klugii "Montenegro Clown" Licensed under CC0 1.0
Porcellio
More oval shaped, prolific isopods native to the Old World, porcellio isopods, also known as European woodlice, are another great cleanup crew option. These tolerate midrange humidity, and are more fast-moving than their armadillidium counterparts. As a result, these
are usually recommended for more arid bioactive setups. Being protein-hungry, however, they need ample food to curb nibbling, as they can even munch on human flesh if given a finger and particularly curious. Don't worry though- they don't maliciously attack! They're just hungry
little bugs, and without proper feeding, can nibble on reptile toes and tail tips. The best known for this habit are porcellio laevis, 'dairy cows', and some species of p. scaber. These are also prolific breeders, so ensure ample space and food.
Porcellio scaber Licensed under CC0 1.0
Porcellionides
Another member of the porcellionidae family, p. pruinosus, also known as 'powder' isopods, are just as prolific, if not more so, than their counterparts. Equally hungry and speedy, these come in a few more colors. Powder blue and powder orange isopods are commonly utilized,
once again, in arid or temperate setups.
Porcellionides pruinosus "powder blue" Licensed under CC0 1.0
Trichorhina
Trichorhina tomentosa, or dwarf white isopods, are small, quite prolific eaters and breeders, and can get fat with ample food supply. Moisture-loving, these are well adapted for tropical tanks. Be warned, however, that these are quick eaters, outcompeting slower-breeding species, especially
cubaris isopods, which are slower, generally.
Trichorhina tomentosa Licensed under CC0 1.0
Cubaris
First discovered in Thai limestone caves just under a decade ago in 2017, these are what's 'hot' in the isopod trade currently. The least 'practical' cleanup isopods, these are slow-moving and slow-breeding for the most part, but they make up for this with their striking patterns and adorable duck-billed faces.
Cubaris sp., or 'duckies', as they're more lovingly known, aren't particularly protein-hungry in comparison to dairy cows and other porcellionidae, and some have gestation times of up to three months, allowing them to be easily outcompeted by other species if cohabitated (NOT RECOMMENDED).
They are particularly humidity-loving, however, but as a result are deceptively easy to accidentally kill- they must have a properly maintained moisture gradient of about room ambient humidity to a moist zone upwards of 70-80%. They also require quite enriched soil.
When building an arid bioactive tank, one must choose the appropriate plants, substrate, and cleanup crew (CUC). As for plants, nontoxic succulents, snake plants, spider plants, and aloe are good options to establish a root system.
Substrate should consist of a sandy soil mixture, made with about a 60-40 mix of an organic topsoil-horticultural charcoal blend and certified quartz sand. Calcium carbonate is not recommended as it causes impaction when wet, and isn't
a great consistency for plant growth. With this, a cleanup crew of arid springtails and Spanish porcellio isopods such as porcellio dilatatus that can deal with heat and low humidity to clean reptile waste and nitrify soil.
An ample supply of cork bark should be present for isopod consumption, and humidity should be low-to-mid level, to prevent the isopods from desiccating. Each bioactive tank should have a 1-2' drainage layer of pebbles or expanded clay balls
separated with mesh from the substrate to allow for any excess water to be drawn back to the surface for plant use.
Tropical Vivariums
In a tropical vivarium, there are more plant options to consider to hold humidity, including pothos, bromeliads, fittonia, calathea, creeping fig, tilandsia, small or micro ferns, snake plants, spider plants, etc. Substrate should be a hearty
mixture of organic topsoil, horticultural charcoal, New Zealand sphagnum moss, decaying cork bark, and an ample layer of leaf litter on bottom, complete with a false-bottom drainage layer beneath the substrate made of expanded clay balls or pebbles,
to allow for water recirculation. An appropriate cleanup crew consists of temperate springtails as a baseline, and from there, there are a few isopod pairing options. For mid-upper humidity, utilize zebra isopods and/or a. vulgare in combination with dwarf whites. For
higher humidity, dwarf whites are still a go-to, but paired with oniscos asellus European woodlice, or, if there is ample space and food, cubaris sp. "panda kings", or more cheaply, cubaris murina, but note that every species of isopod needs a dry spot in their
moisture gradient to migrate to should their gills need drying out- all except dwarf whites. If you plan on having an excessively humid enclosure for, say, dart frogs, stick with springtails and dwarf whites.