Isopods are basically a fancy name for rollie polys, pillbugs, or woodlice. They are small invertebrates, with most species measuring from 1/8″-1″ or so.

There are thousands of species worldwide, with several dozen being cultivated in captivity. Technically, isopods are a terrestrial type of crustacean – they’re more closely related to shrimp than insects!

Isopods live in a wide variety of habitats (some even swim, or live in saltwater), but the ones we’re interested in primarily live on and in the soil in tropical or subtropical habitats.

Once introduced into the substrate and given time to establish, they play several important roles to help keep the habitat fresh and clean:

• Aerate the soil – as they move around, isopods will dig small tunnels and create voids in the soil, allowing air to descend further down into the substrate layer. These voids facilitate plant growth and help keep your substrate from getting waterlogged.
• Consume waste – isopods will eat fecal material, decaying plant matter, wood, and deceased feeder insects that your pet may have missed. They’ll help quickly break down harmful waste into less harmful products that plants can use.
• Make nutrients more available to plants and fungi – not only do isopods break down waste into more usable types of nutrients, but they also disperse those nutrients throughout the substrate as they dig and move about the vivarium. Plants and fungi can then break them down further, keeping your habitat healthier.
• Fertilize plants – What goes in, must come out. Fortunately, what comes out of isopods is great to spur healthy plant growth.
• Eat mites and pest eggs – isopods will predate on the occasional pest eggs. They won’t touch reptile or amphibian eggs, but small eggs (such as from mites) are fair game. They’ll help keep pest numbers down in your bioactive enclosure.
• Act as a supplemental food source – Many animals, especially dart frogs and small lizards, will predate on isopods. With all the benefits that isopods bring to the bioactive terrarium, this may seem like a bad thing, but occasional snacking generally has little impact on the isopod population as a whole.

With all of the benefits, there really isn’t a reason to NOT add isopods in your terrariums.