Isopods get most of what they need from a base diet of leaf litter and rotting wood, but two supplements earn a regular place: calcium, kept in the tub permanently, and protein, offered once or twice a week. A handful of other extras get suggested around the hobby - mineral sources, spirulina, even prebiotics - and a few are worth offering for variety, while others you can safely ignore. This guide runs through what actually helps, what's optional, and what to skip.
Think of supplements as additions to a good diet rather than the diet itself. The foundation is always decaying plant matter, covered in our guide to a healthy diet for isopods; everything below sits on top of that.
Calcium
Isopods build a calcified exoskeleton and shed it repeatedly throughout life, so keep a permanent calcium source in every enclosure, laid on the surface or worked through the substrate and topped up as it is used.
The easiest options are cuttlebone (which also carries trace minerals such as magnesium, zinc and iron), oyster shell and limestone, with crushed eggshell as an occasional extra. Limestone is especially worth knowing about for Cubaris: keepers often add it to their tubs. Simply break cuttlebone into pieces and leave it in the enclosure, or keep a small pile of crushed shell topped up.
Protein: Once or Twice a Week
Most keepers add a little protein once or twice a week. In the wild isopods scavenge animal matter - dead insects and the like - so keepers offer a protein food in captivity too. It doesn't need to be in every feed, just regularly available.
Common choices are whole-animal and fish-based: fish flake, dried shrimp, krill, and black soldier fly larvae are all readily taken and, being dried, hold up better against mould than fresh food. Dried shrimp has the bonus of supplying calcium as well as protein. Our guide to feeding isopods fish flakes covers this in more detail.
One important caveat the older advice often misses: more protein is not always better. Too much - and grain-based foods like fish pellets or dog and cat food in particular - readily attracts grain mites and grows mould in a humid enclosure. So offer protein in small amounts a couple of times a week, use a piece of bark or a slate as a feeding spot so leftovers are easy to remove, and take out anything uneaten after a day or two. (You may also see soy or whey protein powders suggested; they're not something most experienced keepers bother with, and whole-animal sources are both more natural and less troublesome.)
Vegetables and Fruit: Useful Variety
Fresh vegetables and the occasional bit of fruit add vitamins, minerals and welcome variety. Good choices include leafy greens, carrot, cucumber, courgette and squash, with small amounts of apple, banana or other fruit now and then. Keep fruit modest, as its sugar attracts flies and moulds quickly, and remove fresh food before it spoils. These are a supplement to the leaf-litter base, not a replacement for it - see our guide to feeding isopods fruit and vegetables for more.
What About Minerals, Spirulina and Prebiotics?
Beyond calcium and protein, a varied diet generally covers an isopod's needs without much fuss, but a few extras come up often enough to be worth addressing:
- Trace minerals. Isopods do use trace minerals like magnesium and iron, but a varied diet of leaf litter, wood, veg and a calcium source normally supplies them. A light dusting of spirulina powder is a reasonable way to add minerals and a little protein - but it's an optional nicety, not a necessity, and we know of no evidence that it deepens a morph's colour.
- Worm castings. A small amount mixed into the substrate adds microbial life and trace elements and is a useful, natural enrichment.
- Aquarium salt. You'll occasionally see this suggested for trace elements. It isn't necessary for terrestrial isopods and is easy to overdo, so it's one to skip.
- Prebiotics and plant fibres (flaxseed, oat bran, psyllium). These are sometimes promoted for gut health, but the leaf litter and rotting wood isopods already eat provide all the fibre they need. There's no real need to add processed fibre supplements, and overdoing them does more harm than good.
The short version: get calcium and protein right, keep the diet varied, and you don't need a cupboard full of supplements.
Building a Simple Supplement Routine
An easy, reliable approach looks like this: keep a permanent calcium source (cuttlebone or limestone) in the enclosure at all times; offer a small protein feed once or twice a week; add fresh veg and the occasional fruit for variety; and optionally dust in a little spirulina or mix in worm castings now and then. Always remove uneaten fresh food before it moulds, and let the leaf litter and wood base tick away in between. That covers the feeding routine.
Frequently Asked Questions
What supplements do isopods actually need?
Two belong in every routine: a permanent calcium source (cuttlebone or limestone), because woodlice build a calcium carbonate cuticle, and a regular protein source (fish flake, dried shrimp) once or twice a week. Everything else is optional variety.
How do I give isopods calcium?
Leave a calcium source in the enclosure permanently - break cuttlebone into pieces, or keep a small pile of crushed oyster shell or limestone topped up. Crushed eggshell makes an occasional extra.
What is the best protein source for isopods?
Whole-animal and fish-based sources like fish flake, dried shrimp, krill and black soldier fly larvae. They're readily eaten and, being dried, resist mould. Offer small amounts a couple of times a week.
Can you give isopods too much protein?
Yes. Excess protein - and grain-based foods like fish pellets or pet food especially - attracts grain mites and grows mould in humid enclosures. Feed modestly and remove leftovers within a day or two.
Do isopods need vitamin or mineral supplements?
Not usually. A varied diet of leaf litter, wood, vegetables and a calcium source supplies what they need. A little spirulina or worm castings is a reasonable optional extra, but processed mineral or prebiotic supplements aren't necessary.
Do I need special isopod food?
No - though commercial isopod blends exist and are convenient. A base of leaf litter and rotting wood, plus calcium, occasional protein and some fresh veg, covers everything a colony needs.
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