Ever looked down as you walked through a forest? Under your feet are layers of decomposed and decomposing leaves, branches, and so much more. Fun fact: the reason we see leaves, tree trunks, and complete plants in coal seams is that the things that help to decompose plants evolved to eat them after the plants evolved. One of these decomposers is the isopod — and understanding their diet is one of the most important parts of keeping a thriving colony.
This guide pulls together what the actual research tells us about isopod nutrition, with practical guidance on what to feed your colony in a UK setting. References to peer-reviewed studies are included throughout — useful both for keepers who want to dig deeper and for getting the science right rather than relying on hobby folklore.
Quick Answer: What Do Isopods Eat?
Isopods are detritivores whose primary food is partly decomposed leaf litter from flowering plants and trees. They also eat rotting wood, decaying organic matter, weed leaves (dandelion, nettle, sow thistle), small amounts of fruit and vegetables, occasional protein from insects or quality fish food, and calcium from sources like cuttlebone, eggshell, or limestone. Crucially, they need microbes on their food to digest it properly — sterile food is poor food. Diet quality directly affects breeding success, with high-protein and high-carbohydrate diets producing different reproductive outcomes (Lardies et al. 2004).
Do Isopods Eat Leaf Litter?
The main part of an isopod's diet is leaf litter — and studies have shown they prefer partly decayed leaf litter, not fresh leaves. This is because partly decomposed leaves are already partly broken down and easier for them to digest (Zimmer 2002). Whilst isopods do have digestive enzymes of their own, they need the microbes on the food to help it break down and to extract maximum nutrition. This is why "fresher is better" doesn't apply to isopod food the way it does to most pets.
Studies in the late 80s found that isopod growth was best when they were fed on partly decomposed leaves of dicotyledonous plants (Rushton & Hassall 1987). This is a huge chunk of the flowering plants and trees in the world. In that study, freshly fallen leaves of flowering plants led to population booms, but populations only fed on 3-month-old grass saw a population crash. Plant choice matters significantly more than many keepers realise.
Interestingly, isopods will choose the food that they perceive as being the most nutritious and will stop eating when they've had enough of the nutrients they need. Most species will select leaves with higher protein levels — they're surprisingly capable of self-regulating intake when offered variety.
There's a notable trade-off in breeding nutrition that's worth understanding. When breeding, isopod females on a high-protein diet had smaller offspring, although in higher numbers. High-carbohydrate diets led to females releasing fewer mancae, but incubating them for longer — and the resulting offspring were larger than the high-protein group (Lardies et al. 2004). Neither extreme is "better" — a varied diet that gives the females options is what actually works.
Where to Find Leaf Litter for Isopods
Leaves on trees have a much higher protein content than fallen leaves, and as the season progresses the protein content reduces (Forwood & Owensby 1985), so fallen autumn leaves dried and kept year-round might not be the best food on their own — though they're still a great starting point and the foundation of most setups.
For food (rather than substrate or bedding), consider adding the leaves of flowering weeds. Dandelion, sow thistle, and nettle work brilliantly — blanch nettle in a bit of boiling water first or let it dry out completely to neutralise the sting. Field bindweed, hedge bindweed, and many other weed sources are great additions. Just make sure to:
- Collect from places that haven't been chemically sprayed — pesticides and herbicides are poisonous to isopods and many take years to break down
- Stay a safe distance from roads — trees are excellent at removing heavy metals from the air and storing them in their leaves; collecting roadside leaves means feeding heavy metals to your colony
- Avoid suspect sources — anywhere that could have been treated, gritted, or contaminated
Fresh maple, oak, and chestnut leaves are also good additions. For UK keepers who'd rather skip the foraging, PostPods stocks Leaf Litter sourced from clean, untreated UK woodland — ready to use, with no contamination risk.
Should I Feed My Isopods Fish Food?
So if a high-protein diet supports growth, fish flakes must be the answer, right? Take a second before grabbing that pot of cheap flakes.
Cheap fish food is often based on a mix of fish meal and wheat — and as we covered above, isopods fed on grass do not do well. There's often around 50% protein in fish flake. By contrast, dried nettles and dandelions are about 30% and 20% protein respectively, and they're a more natural source of nutrition than fish meal — closer to what isopods actually evolved to eat.
This isn't to say you should stop feeding fish food, just that you should select a good quality pellet rather than cheap flakes. The better foods now have a percentage of insect meal rather than just fish meal, which is much closer to what isopods would encounter in the wild. Feed it as part of a larger, varied diet — not as the main course.
Should I Feed Fruit and Veg?
Isopods don't need a lot of carbohydrates in their diets, so sugary fruits shouldn't make up a huge part of what you feed them. But some shredded carrot, courgette, sweet potato, or similar will often go down well. A varied diet allows isopods to self-select what they need.
A few practical notes:
- Carrot and sweet potato are well-tolerated and contain useful carotenoid pigments that support colour expression in orange/red morphs
- Courgette and cucumber are fine — despite some older articles claiming otherwise, isopods of all popular species eat both
- Avoid citrus — too acidic, generally rejected
- Banana and mango in small amounts are fine and often appreciated
- Remove uneaten fresh food after 24 hours to prevent mould
Do Isopods Eat Insects?
You'll see plenty of suggestions about feeding isopods shrimp or dried fish, and in small amounts that's fine. But we know from research on fish that feeding the wrong sort of protein can lead to disease, probably due to imbalanced fatty acids in the diet, so it's worth choosing food that mimics their natural diet.
In the wild, isopods do hunt and eat small insects, as well as helping to break down dead ones. So look for:
- Dried crickets or similar invertebrates
- Insect-based fish food (more available now than even a few years ago)
- Half a cricket or other feeder insect dropped in (if you keep reptiles or arachnids that get fed insects)
The exoskeleton of insects is also a great natural source of calcium for isopods — a useful side benefit.
Do Isopods Eat Their Own Faeces?
Remember that bit about isopods needing microbes to help them digest their food? That's why they practice coprophagy — faeces eating, both their own and other animals'. Yes, it's a bit grim, but they're far from the only animals to do this (rabbits and rodents are well-known practitioners too). It's not something you need to worry about or try to prevent — unless you're polishing every surface in their enclosure daily, which would actively harm the colony.
There is some genuine benefit to adding nitrogen-rich faeces to an isopod's diet, but studies have shown this isn't something you need to actively source. There's also a real risk of contamination from random faecal matter — bagged "guano" sold for the garden may have come from seabirds, which can have a high heavy metal content.
One important exception: cave-dwelling isopods. Cave ecosystems are fascinating, but the base of the food web there isn't plants — it's bird or, more often, bat guano. For Cubaris and other cave-dwelling species, a small amount of properly sourced bat guano is genuinely beneficial. Just make sure you source it sustainably — many cave ecosystems are suffering as guano is collected as fertiliser, and ethical sourcing matters.
Calcium
In general, if you give your isopods a varied diet, they'll be getting plenty of calcium — but it's worth giving them a dedicated, accessible source they can use whenever they need it (particularly during moulting and breeding).
Three solid options:
- Eggshells — a great source of bioavailable calcium; in mammals, eggshell calcium is absorbed as easily as pure calcium supplements. Free if you cook your own eggs
- Cuttlebone — soft, easy for isopods of all sizes to graze on. PostPods stocks Cuttlebone in 100g packs
- Limestone rock — slow-release, doubles as habitat structure. See our limestone for isopods guide for the full picture
For most keepers, having both cuttlebone and limestone in the enclosure provides the best of both worlds — soft, accessible calcium plus long-lasting habitat-grade calcium that buffers the substrate pH.
Diet for Pet Isopods (Display Species)
If you're keeping isopods for their own charms — as display animals rather than just bioactive cleanup crew — there's room to do some genuinely interesting research into their natural diets. Worth thinking about:
- What plants are native to the area these isopods are from? Mediterranean species evolved alongside oak, olive, and pine; Vietnamese Ardentiella alongside specific tropical plant communities
- Have they evolved to live in caves alongside bats or birds? Cave species genuinely benefit from guano supplementation
- Are they limestone-cliff specialists? Cubaris and Spanish Porcellio particularly benefit from carbonate-rich substrates
Above all, feeding a variety of foods, based around fallen leaves and small amounts of other naturally occurring foods, will help you keep a thriving colony.
Isopods as a Bioactive Cleanup Crew
If you have a bioactive vivarium for reptiles, amphibians, or arachnids, isopods are probably already on your list. We'd particularly suggest the Porcellionides pruinosus range (Powder Orange, Powder Blue, etc.) or the classic favourite Dairy Cow isopods (Porcellio laevis) — both prolific, hardy, and excellent at their cleanup duties.
Isopods will help break down leftover food, waste, bedding, and everything else organic in the enclosure. Often the bedding you're using for your reptile or other primary animal already contains foodstuffs for the isopods. Consider adding springtails as well — together, isopods and springtails form an exceptionally effective cleanup crew that processes food at different particle sizes.
Frequently Asked Questions
What's the main food for isopods?
Partly decomposed leaf litter, supplemented with rotting wood and a small amount of vegetables, fruit, and protein. The microbial communities developing on partly decayed leaves are essential — isopods can't digest fresh plant material as efficiently as decomposing material.
Can I feed my isopods only fish flakes?
No — and you shouldn't. Fish flakes are useful as part of a varied diet but shouldn't be the foundation. Cheap fish flakes contain too much wheat (low nutritional value for isopods) and the wrong protein profile. A good-quality pellet with insect meal is better, fed alongside leaves, vegetables, and other natural foods.
Do isopods eat poop?
Yes — they practice coprophagy, eating their own faeces and that of other animals. This is normal, beneficial (helps with microbial digestion), and not something to prevent. The exception is bat guano, which is genuinely beneficial for cave-dwelling species like Cubaris but should be sourced sustainably.
What fruits and vegetables are best for isopods?
Carrot, courgette, sweet potato, cucumber, squash, and small amounts of apple, banana, or mango all work well. Avoid citrus (too acidic) and anything that's been sprayed or treated. Remove uneaten fresh food after 24 hours.
How often should I feed my isopods?
Foundation foods (leaf litter, rotting wood, calcium) should always be available in the enclosure. Fresh vegetables and protein are best offered twice weekly. Don't overfeed — most nutrition comes from the substrate itself, and excess fresh food encourages mould and grain mites.
Where can I buy isopod food in the UK?
Browse our accessories collection for clean, ready-to-use isopod food and substrate components — leaf litter, rotting wood, cuttlebone, and more, all sourced specifically for invertebrate use.
Final Thoughts
The best isopod diet isn't complicated, but it does need to be varied. Build the foundation around partly decayed leaf litter and rotting wood (which the isopods graze on continuously), add fresh vegetables and occasional protein twice a week, keep calcium constantly available, and let the isopods self-select what they need. The research consistently shows that variety matters more than precision — colonies given options thrive; colonies stuck on a single food type underperform regardless of which food it is.
Browse our accessories collection for the components needed to feed a thriving colony — leaf litter, rotting wood, cuttlebone, and more — all clean, ready-to-use, and sourced specifically for UK isopod keepers.
References
Forwood, J. R., & Owensby, C. E. (1985). Nutritive value of tree leaves in the Kansas Flint Hills. Journal of Range Management, 38(1), 61–64.
Lardies, M., Carter, M., & Bozinovic, F. (2004). Dietary effects on life history traits in a terrestrial isopod: The importance of evaluating maternal effects and trade-offs. Oecologia, 138, 387–95. doi:10.1007/s00442-003-1447-5
Rushton, S. P., & Hassall, M. (1987). Effects of food quality on isopod population dynamics. Functional Ecology, 1(4), 359–367. doi:10.2307/2389792
Zimmer, M. (2002). Nutrition in terrestrial isopods (Isopoda: Oniscidea): an evolutionary-ecological approach. Biological Reviews, 77(4), 455–493. doi:10.1017/S1464793102005912
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