Isopods kept in terrariums fall into roughly seven genera — Armadillidium, Cubaris, Porcellio, Porcellionides, Merulanella, Trichorhina and Oniscus. They are land crustaceans, not insects, and the practical difference between them comes down to three things: whether they roll into a ball, how much moisture they need, and how fast they breed.
Quick answer
There are around 4,000 described terrestrial isopod species worldwide, but fewer than a hundred are kept with any regularity. For a bioactive terrarium the choice usually comes down to a Trichorhina or dwarf species for a clean-up crew that stays out of sight, an Armadillidium for a visible display animal that tolerates a drier enclosure, or a Cubaris if you want a slow-breeding, high-value species and are prepared to hold humidity steady.
What an isopod actually is
Isopods are crustaceans in the suborder Oniscidea — the only crustacean group that has fully colonised land. They breathe through pseudotracheae, structures in the rear limbs that only work when damp, which is why every husbandry decision below comes back to moisture. They carry eggs in a fluid-filled pouch called a marsupium and give birth to live young called mancae, so you will often see a colony expand without ever seeing an egg.
Because they are crustaceans they need calcium to harden a new exoskeleton after every moult, and they moult in two halves — back first, then front. An isopod that looks half-pale is mid-moult and healthy, not sick.
The main groups, and what separates them
Armadillidium
The classic “pill bug”. Conglobates fully into a sphere, tolerates a drier substrate than most, and breeds readily. Armadillidium maculatum (Zebra), A. klugii and A. vulgare are the usual entry points. Good display animals because they sit on the surface rather than burrowing out of sight.
Cubaris
The genus behind most of the high-value trade names — Rubber Ducky, Panda King, Amber Ducky. Slower to reproduce, more sensitive to a humidity crash, and generally more expensive as a result. Most require a deep moist layer and a genuine moisture gradient rather than a uniformly wet enclosure. Note that a great many animals sold as Cubaris are undescribed and the genus placement is provisional.
Porcellio
Large, fast, and mostly non-conglobating. Porcellio scaber, P. laevis and P. hoffmannseggi are the common ones. They are the workhorses of a clean-up crew because they process leaf litter quickly and breed hard, but they will climb and they need more ventilation than a Cubaris.
Porcellionides
Porcellionides pruinosus — the Powder species — is unusually fast-moving and coated in a waxy bloom. It reproduces very quickly and tolerates a wide range of conditions, which makes it one of the more forgiving clean-up crews for a first bioactive build.
Merulanella
Small, brightly patterned, and the least forgiving group in common culture. They want stable high humidity and cool temperatures, and colonies crash quickly if a setup dries out. Not a first isopod.
Trichorhina and other dwarfs
Trichorhina tomentosa, the dwarf white, is parthenogenetic — a colony of one animal will populate an enclosure. They stay in the substrate and are almost never seen, which is exactly what you want in a clean-up crew that sits under a gecko or a millipede rather than being the display animal itself.
Oniscus and Philoscia
Temperate species, often collected locally. Oniscus asellus is large, flat and hardy. Useful and cheap, though rarely the reason anyone builds an enclosure.
Comparison at a glance
| Genus | Conglobates | Moisture | Breeding speed | Best used as |
|---|---|---|---|---|
| Armadillidium | Yes | Low to moderate | Fast | Display |
| Cubaris | Yes | High, stable | Slow | Display / project |
| Porcellio | No | Moderate | Fast | Clean-up crew |
| Porcellionides | No | Moderate | Very fast | Clean-up crew |
| Merulanella | Partial | High, stable | Slow | Advanced project |
| Trichorhina | No | High | Very fast | Hidden clean-up crew |
What every group needs
The husbandry is more similar than the price differences suggest. All of them want a moisture gradient — one damp end, one dry end — rather than a uniformly wet box. All of them need calcium available at all times, as cuttlebone, crushed eggshell or limestone; calcium deficiency is one of the most common causes of failed moults in captivity. All of them need leaf litter and decaying hardwood as the base of the diet, supplemented occasionally with a protein source. That substrate requirement is the same logic that governs millipede care, and the enclosure principles carry over almost unchanged — see our guide to building a millipede enclosure.
The one thing isopods will not tolerate is stagnant, saturated substrate with no airflow. Ventilation is not optional.
Choosing for a bioactive terrarium
If the isopods are there to do a job — breaking down waste under a gecko, a millipede or a snail — pick a fast-breeding species that stays in the substrate. If they are the point of the enclosure, pick something that sits on the surface where you can see it. Mixing two species in one enclosure usually ends with the faster breeder dominating, so run them separately unless you have a specific reason not to.
We keep clean-up crews in the same bioactive systems as the rest of the collection, and the substrate and hardscape we use are in terrarium supplies. Our live invertebrates are listed under invertebrates, and every animal that ships from us is covered by our live arrival guarantee.
A note on names
A large share of the isopods in the hobby carry trade names rather than valid binomials, and some are genuinely undescribed. We state a binomial where one exists and say plainly where it does not, and every animal we hold gets an accession record in the SpeciesVault registry so its origin and lineage can be cited rather than claimed. You can read why we work that way on our about page.
Rubber Duckies are now in stock. The most requested Cubaris in the hobby is available from our own captive-bred colonies — see Cubaris sp. “Rubber Ducky” isopods, offered in 6, 12 and 20 counts.
Common questions
Are isopods insects?
No. Isopods are crustaceans, more closely related to crabs and shrimp than to any insect. They breathe through modified rear limbs that must stay damp, which is why humidity matters more for them than for most terrarium invertebrates.
Which isopod is best for a beginner?
Porcellionides pruinosus or Armadillidium vulgare. Both tolerate a range of conditions, breed quickly enough that early mistakes are recoverable, and do not require the stable high humidity that Cubaris and Merulanella need.
Why are Cubaris isopods so expensive?
They breed slowly, produce small broods, and many of the popular forms are still undescribed and collected from limited localities. Price reflects reproduction rate and supply, not difficulty of care in itself.
Do isopods need calcium?
Yes. They are crustaceans and must rebuild a mineralised exoskeleton at every moult. Cuttlebone, crushed eggshell or limestone should be permanently available. Failed moults in a colony are usually a calcium problem before they are anything else.
Can isopods live with millipedes or geckos?
Yes, and that is the most common reason to keep them. A dwarf white or Porcellionides colony will process waste in the substrate without disturbing the display animal. Keep the substrate deep enough for both and do not let the enclosure dry out completely.