Culturing Isopods and Springtails

Isopods and springtails are the only things on a feeder list you are not supposed to use up. You buy them once, they breed in a box on a shelf, and if the box is right they keep producing for years. That makes them the cheapest thing in the cupboard over time and the one most often killed in the first month, because everything that works for a cricket bin is wrong here. This guide covers setting up and holding both cultures. The Bug Cartel does not sell isopods or springtails, so it is written for keepers who source a starter culture elsewhere.

Two animals, one requirement, opposite tolerances

Both are moisture-dependent, and that is where the similarity ends.

Springtails want the substrate wet enough that the air above it is saturated. Standard laboratory culture keeps them on a moist plaster-and-charcoal base at around 20 °C, in a closed container, fed dry baker's yeast about once a week. The substrate is kept moist but not waterlogged. That is a wetter environment than anything else you keep.

Isopods want the opposite of uniform. Laboratory populations of Armadillidium vulgare have been held on damp soil and deciduous leaf litter at roughly 20 to 25 °C, and Porcellio scaber at around 24 °C in gauze-covered containers with the soil kept damp. What the hobby has converged on, and what matters more than any single number, is a moisture gradient: one end of the box wet, the other end dry, and the animals choosing. A box that is uniformly soaked stagnates and molds; a box that is uniformly dry kills them slowly.

Setting up an isopod culture

The box is a ventilated plastic tub with a deep substrate and a lot of cover. Depth matters here in a way it does not for feeder bins, because the substrate is where they live rather than something to clean off the floor.

• Substrate. A soil-based mix that holds moisture without going to mud, several inches deep. Coconut fibre, leaf mold and a little sphagnum are the usual components.
• Leaf litter on top. This is food and cover at once, and it is not optional. Dried deciduous leaves, replaced as they get eaten down.
• Cork bark or a hide. Isopods spend most of their time underneath something.
• A calcium source, permanently. Cuttlebone or crushed oyster or egg shell. The isopod cuticle is calcium-carbonate reinforced, molting depends on it, and a culture without it stalls.
• A moisture gradient. Water one end. Do not water the whole box.
• Ventilation, but not much. Enough to stop the air going stale, little enough to hold humidity.

Feeding is leaf litter plus a protein or vegetable supplement on a small scale: a piece of fish flake, a dried shrimp pellet, a slice of vegetable, offered on a lid rather than buried. The rule is that anything not eaten within a day or two comes out.

Setting up a springtail culture

Simpler, and easier to get wrong in one specific way.

Two setups are standard. The laboratory one is a plaster-of-Paris and charcoal base, kept moist, in a lidded tub; the black base makes the white springtails visible, and the charcoal absorbs waste. The hobby one is a tub of moist substrate, usually coconut fibre or charcoal chunks, with a shallow layer of water at the bottom. Both work. What they have in common is a closed container and a substrate that stays damp without free-standing water over the animals.

Food is a dusting of dry yeast, roughly weekly. Some keepers use uncooked rice or mushroom instead. All three go moldy if you overfeed, and mold is the failure mode in a springtail culture almost every time. Feed a smaller pinch than looks right.

Harvesting is the other half of the design. With a water-bottomed tub, tapping the sides floats springtails onto the surface and they can be poured off. With a substrate tub, a piece of bark or a lid laid on the surface will collect them underneath. Either way, do not harvest a culture down; take a portion and leave the rest to rebuild.

Temperature: room temperature, and no heat

Neither of these wants a heat mat. Springtail cultures run at 20 °C in the laboratory, and the published isopod work sits in the low to mid twenties. That is ordinary indoor temperature in most homes.

Heat is the specific risk. A closed, humid container on a heat source is a very effective way to cook a culture, and because both animals are hidden in substrate you will not see it happening. If a culture has to sit near a warm bin, put it at the bottom of the shelf rather than the top.

Cold is a slower problem. Both slow down and stop breeding as it gets cool, and a culture in an unheated garage over winter usually survives and produces nothing.

How long a culture takes, and how long it lasts

This is where the expectations go wrong, so it is worth being blunt about it.

Isopods are slow. A starter culture that arrives as a couple of dozen animals is not a feeding source for a season, and treating it as one is how people conclude they died. Buy the culture well before you need it, or buy enough to feed from immediately and accept that you are buying feeders rather than a colony.

Springtails go the other way. A culture can go from a starter portion to a harvestable population in weeks, which is why they work as a first food for tiny animals and as clean-up crew in a bioactive enclosure at the same time. Keepers of frogs, other amphibians and crested geckos usually run more than one culture for exactly this reason: one to harvest and one to leave alone. While a culture builds, wingless fruit flies are the smallest feeder we sell. Small insects carry more supplement dust for their size than large ones, and our gut loading guide covers dusting.

What goes wrong

• Mold across the surface. Overfeeding, nearly always. Remove the food and the moldy substrate, and feed less. A little mold on a food item is normal; a mat of it is not.
• Mites. Fast-moving pale mites in a damp culture are common and usually harmless competitors that arrived with overfeeding. Grain mites in the leaf litter are the same story. Cut the food and increase ventilation before doing anything drastic.
• An isopod culture that stops producing. Check calcium first, then leaf litter, then whether the box has gone uniformly wet or uniformly dry.
• A springtail culture that empties. Usually either mold, or a substrate that dried out while you were not looking. Springtails desiccate quickly.
• A sour, black, anaerobic layer at the bottom. Too much water and not enough air. This one is worth stripping.

When to write off a culture

Rarely, is the honest answer. Both of these recover from a bad month better than any feeder insect, and the usual mistake is throwing out a culture that had gone quiet rather than dead. Before you write one off, sift the substrate properly: isopods hide, and a culture that looks empty on the surface often is not.

Strip and restart when the substrate has gone anaerobic and sour through the whole box, or when a mold mat has taken the surface repeatedly after you have already cut the feeding. In both cases the substrate goes, the box gets washed and dried, and whatever animals you recover go into fresh material.

A culture that arrives dry, hot, or with the substrate collapsed is an arrival problem rather than a husbandry one, and isopods and springtails in particular can look completely lifeless while being fine. If the seller has a live arrival window, photograph the culture on arrival before anything else, then give it a settled, correctly moistened box and a few days before you judge it. Our guide on what to do when your feeders arrive covers the unpacking sequence for the feeders we ship.

Where to go next

Cultures are the one part of a feeder setup that gets cheaper the longer you leave it alone, which makes them worth the shelf space even if they are not your main feeder. Setting up a feeder storage station covers where a humid, unheated culture box goes relative to everything else, and the feeder range covers the live feeders we sell to sit alongside a culture.