First off, I’m going to set the stage of where I first started catching and finding isopods: these are animals that literally thrive underneath my garbage cans. Yes, I collected eight separate species from underneath my garbage cans. Their diet is not the tricky aspect of isopod keeping.
Leaves that have been stripped down to the veins by Porcellio scaber.
So, what do isopods eat? Isopods are detritivores meaning that they are nature’s cleaners – and they will eat anything and everything (dead, not alive). The kicker here is that they eat organic components, so animal carcasses, leaf litter, rotting wood, etc. Their diet also expands into the slightly unconventional, as they eat decaying cardboard, animal hair, and some weirdos keepers state that isopods will eat human nail clippings and cast away skin.
A balanced diet is an important part of any healthy animal’s life. In order to thrive, isopods should have a base diet and a constant source of leaf litter. What kind of leaf litter? Well, in 5 years of keeping isopods I have yet to encounter a variety of leaf litter that people have reported to have caused death to their cultures. However, if you are unsure, I recommend offering the leaf litter to a small starter culture for one month and observing for culture crash or die offs before offering as a main source to the remaining cultures. This way, if there is a loss, it is greatly reduced. We have used cottonwood, linden, elm, maple, oat, magnolia, willow, and Russian olive leaves in our cultures with great success. We’ve also used various types of evergreen needles that the isopods have happily consumed. Other keepers have reported using honey locust, alder, poplar, hibiscus, forsythia, birch, chestnut, beech, pecan, mesquite, apple, palm, murbei, cedar, sycamore, ash, alder, ailanthus, zelkova, ficus, fig, and plum tree leaves. The only instance I have personally have had an issue is when leaves were compressed in a moist area over time and began to smell of ammonia due to lack of oxygen as they decayed. These leave did actually kill the isopods they were offered to. If the leaf litter smells of ammonia, I recommend not using it.
In recent years, isopod specific substrate has been marketed as a replacement for leaf litter. We do not recommend using enriched substrate as the primary diet. While it is true that enriched substrate is extremely beneficial to isopod cultures, it cannot be a replacement for leaf litter. Isopods do eat enriched substrate, they’re basically really expensive vegetable plants. They benefit from natural fertilizers like potash, sphagnum moss, peat humus, bat guano, mycorrhizae, compost, gypsum, and shrimp meal. The only item we recommend avoiding is “plant food” release capsules that are often in soils; these are not harmful to the isopods but can be harmful to reptiles or abrasive to keeper’s hands.
The next item we recommended offering isopods is softened wood. Previously, it was recommended to avoid softwoods like evergreens, because these are natural insecticides, but many isopods actually prefer evergreens as a source of food. This is because isopods are crustaceans, not insects, so the wood is not harmful to them. It is important to make sure to not offer them fresh wood because the thick tree sap can bleed and trap the animals, but otherwise they thrive on all decaying wood.
Isopods should be supplemented with protein sources to encourage populations to stabilize and thrive. They can survive without supplemental protein, but many keepers have noted culture crashes or that the population becomes stagnant and does not grow. Isopods can get protein from a variety of sources- it can be provided in the form of fish pellets or fish flakes, turtle food, dried shrimp, reptile sheds, or animal waste. Isopods will eat any animal waste, but the kicker is that larger waste takes longer for them to break down (large snake waste may take a culture of thousands to efficiently break down). A large isopod colony will even break down animal carcasses- keepers frequently offer mice and rats that have been rejected by snakes. Our Porcellio laevis took out a rat carcass in a matter of days!
Calcium is another item we recommend offering isopods. It is much more important for some species than others- the large Spanish Porcellio and Armadillidium in particular need calcium in order to thrive. Calcium can be derived from multiple sources; the easiest for keepers to offer simply being egg shells. Egg shells do not need to be sterilized- the isopods don’t care, I promise. I do recommend allowing the egg goo to dry as the highly intelligent isopods get trapped in it and perish. A really fun thing to do with egg shells is crush them up in a corner, then check the setup in a few days and the isopods have taken the little egg bits all throughout the setup and into their burrows to munch on later.
Cuttlebone is another calcium source that is offered to isopods; this is consumed much more quickly because it is softer and more readily available. Keepers also offer actual bone fragments; these take a long time to break down due to their density but gradually more and more tiny little bite marks can be observed. In fact, this is why isopods make poor cleaners for use in taxidermy, because they steal the tiny bones first and obliterate them. Elk horn is another option with growing popularity in the hobby, but again takes forever to break down. If it’s preferred not to have an entire bone just vibing in the isopod setup, the bone can be cut or smashed and tossed in for the isopods (it won’t affect the calcium content and may make it more accessible to the isopods).
Fruit and veggies is a nutritional source that is popular to offer isopods. This is the one item in this article that they do not need to thrive, but it does encourage a healthy population. So, what fruit and veggies are safe to offer? All of them. Yes, all of them. They will eat carrots, they will eat cucumbers, squash, peppers, potatoes, greens, apples, grapes, peas, and tomatoes. The only vegetable I offer with caution is potatoes, because if the potatoes manage to grow a shoot, the shoot emits CO2. In an enclosed space, this may suffocate the isopods because CO2 is denser than air. An additional note is that if too many fruits or vegetables are offered, they will mold. In the case of fruits, this is mildly alarming, because a very colorful blue-green mold thrives on the high sugar content of fruits. This will not harm isopods, but it is good practice to remove it because isopod mancae can become trapped in particularly fluffy mold.
Food sources should always be avoided if there is suspicion of poisons or pesticides being used in the area. Foods that are safe for human consumption are safe for isopod consumption- so fruits and vegetables should just get a quick rinse prior to being offered. The concern of pesticides is specific to collecting leaf litter- if there are no invertebrates in the surrounding area (or, invertebrates acting very strangely), do not collect leaf litter for use.