One of the biggest questions that people setting up bioactive enclosures ask is “What are the best isopods for my animal and setup?” There are so many options that it can be a very overwhelming selection. Some isopods may do well in the environment, but breed slowly and are lazy cleaners. Some isopods won’t do well in the environment at all. Even more importantly, isopods may do TOO well and overwhelm the animal.
Crested geckos, and other New Caledonian species of geckos, typically are kept between a range of temperatures between 65F and 80F. This is an ideal temperature range for any isopod, although at 65F, they will have a much lower reproduction rate. These geckos also need a relatively high humidity, most care sheets stating at least 80%, misted daily, with a total dry out period. While the entire substrate won’t dry out in between mistings, the surface area will. A word of caution: it is very easy to overwater geckos in these setups, so monitor the moisture level of the substrate carefully. Substrate that is saturated with water is bad for both crested geckos and isopods.
These requirements are suitable for most common species of isopods. Isopods that should not be used as a cleaner crew are the Spanish giants such as P. haasi, P. expansus, P. bolivari (to name a few) because this environment is too moist for them. The giant Spanish species are also so large that geckos will easily prey on them. Rare Thai Cubaris species, such as the popular rubber ducky, are a poor choice due to their slow breeding behavior.
Crested geckos, and other New Caledonian geckos, have soft, velvety skin. They do have scales, but are not firm like other reptiles’ scales, making them vulnerable. In the best interest of these animals, more docile species of isopods are preferred. The first group of cleaners to choose from are the many dwarf varieties available, foremost being Trichorhina tomentosa, or “dwarf white isopod”. These isopods are an all-female species, reproduce parthenogenetically, and populate a tank quickly. They are efficient cleaners, readily consuming waste, all while harmless to large animals. Dwarf white spend the majority of their time burrowed below the substrate, and are so small that they do not pose a risk of harming or stressing geckos. Other dwarf species that are suitable for these setups include Trichorhina sp. “dwarf purple”, Trichoniscus pusillus, Venezillo parvus, and Agabiformius lentus. All of these dwarves have similar care and behavior to that of T. tomentosa, except that V. parvus and A. lentus are not able to reproduce parthenogenetically. For very small gecko species that stress easily, such as geckos in the Eurydactylodes genus, we recommend only using dwarf species.
When designing a bioactive setup, it is a good policy to have several “layers” of cleaners. The next “layer” of invertebrates that many people add after isopods are springtails. Springtails are often called “cleaners for cleaners,” processing the frass of other invertebrates. There are many springtail species available, typically advertised under common (not scientific) names. Giant white springtails are the most popular, followed by temperate pink and then silver springtails. Pink springtails are the most resilient, thriving in any setup, but the others are useful as well. Whatever species of springtail is used, adding additional kinds is a fruitless endeavor, because one springtail will outcompete the others. All springtails are suitable for addition to gecko setups and will thrive as long as the environment is moist, even if the springtails number into the thousands, reaching swarm conditions, they pose no threat to either the reptile or isopods. Amusingly enough, springtails often establish themselves in setups, whether they are intentionally introduced or not, and may cause a slight panic due to their visual similarity to mites.
Larger species of isopod are also beneficial to gecko setups, especially for large adult crested geckos or the giant New Caledonian species Rhacodactylus leachanius. The safest larger species of isopod commonly used is Porcellionides pruinosus, or “powder blue”. Pruinosus is available in 4 color/pattern variations: orange, blue/gray, white, and pied. Pruinosus is a soft bodied isopod, while still being high in calcium. This trait makes them both an ideal cleaner and a feeder animal. Pruinosus reproduce very quickly in addition to faithfully cleaning waste in their environment. Although they are larger than dwarf species, pruinosus do not hunt or actively seek out other animals (even when swarming or over populated) and are safe to use with soft skinned geckos. In the instance of small, sensitive geckos like Eurydactylodes, it may be best to avoid use of pruinosus, because while they will not intentionally harm the animals, adult isopods crawling over these fragile geckos may upset them enough to the point of death.
Generally, it is recommended that keepers avoid members of the Porcellio genus, although they are hardy, good cleaners and breed well. Porcellio isopods, such as Porcellio scaber, Porcellio laevis, and Porcellio dilatatus are highly efficient breeders and cleaners. So efficient they are notorious for their insatiable appetite and preying on other animals. Some people believe that if isopods are provided adequate protein, this will prevent them from attacking other animals; however, this only delays the inevitable, because if the animals are left unchecked, they will reach swarm conditions and no amount of protein will sate them. I estimate that we have between thirty and forty years left before they conquer the world. Species like scaber and laevis have even been observed committing cannibalism when their setups are overpopulated. Amphibians, having soft skin, are at risk of becoming isopod chow, as well as small terrestrial geckos and even arboreal geckos. Isopods can climb, and unless the tank is three feet tall or more, scabers will find a sleeping animal. These animals can be used safely in bioactive terrariums, just take a bit more care than others. The population should be removed periodically to reduce risk of incidence to the inhabitants, if the resident isn’t keeping them in check already.
Not all isopods are created equal. Isopods inhabit every corner of the globe, but are adapted to certain environments as cleaners. Isopods come in different sizes, shapes, and with different need, so only certain isopods may thrive in your conditions and be suitable roommates for the animals inhabiting them. Choose carefully!