Our springtails came from a big box pet store, twice. The first cup went into the display tank; the second was split across the tubs. We did not note a packed date on either. The isopod package we saved from the same store has an old one on it, so we suspect their live stock sits a while and ours had been sitting too. That is a guess about why they were slow to get going, not something we measured. It is also why we now check the date on anything live before it goes in the cart. They took three or four weeks to show up in any numbers, and then they were everywhere. The first sign it was working was a few grains of rice going fuzzy and gray. That fuzz is the whole trick. Springtails eat mold, so a springtail culture is really a small, controlled mold farm with springtails on it, and once you see it that way the care makes sense.
What springtails are and why you keep a culture
Springtails are tiny white or gray hexapods, a millimeter or two long, that live in damp soil everywhere on earth. The species almost everyone in this hobby keeps is the white springtail, Folsomia candida. They eat mold, fungus, and the film of decay on anything rotting, and they breed constantly, which is why every bioactive tank wants a starter dose of them. The reason to keep a separate culture, rather than just having them in the tank, is supply: a culture is a reservoir you can pour from whenever a new tank, a new isopod tub, or a mold outbreak needs seeding.
The cup
A 16- or 32-ounce deli cup with a lid. Fill it a third of the way with damp coco coir and a scatter of horticultural charcoal mixed through. Keep it wet enough that the coir holds together when squeezed; springtails live on the damp surface and in the air pockets between. Poke a few pinholes in the lid, or none at all if you open it to feed every few days. No topsoil, no leaf litter, no wood. That recipe is for isopods, and it is covered in our isopod substrate recipe; springtails want the opposite, a clean medium where the only thing growing is the mold you feed them.
Charcoal versus coir is a real debate among keepers, and both work. Charcoal drains and is easy to pour from; coir holds more moisture and is what most starter cultures are sold on. Ours is coco coir with a little charcoal mixed in.
Feeding
Drop in a few grains of uncooked rice, or a tiny pinch of brewer's yeast, and put the lid on. The rice molds in a few days and the springtails move onto it. When the grains are eaten down or turn to mush, add a few more. That is the entire feeding routine. Fuzzy grains mean the culture is working; if you see fuzz and feel a flicker of panic, that is the moment to remember you are farming mold on purpose.
The mistake is overfeeding. A spoonful of rice grows more mold than the springtails can eat, the cup goes sour, and mites move in. A few grains at a time, replaced when they are gone. If the cup ever smells sour or the water goes cloudy, pour off the water, rinse the charcoal, and restart from the same cup; there are always enough survivors.
Why you never have to split it
Unlike isopods, a springtail culture is self-regulating. It grows to what the cup and the food can support and then holds there indefinitely, as long as you keep feeding it and keep water in the bottom. You harvest from it and it refills. You only start a second cup to have more supply, not because the first one is in danger. Ours was seeded to boom by October and get split into several cups after that, purely to have more to pour from, not for the health of the culture.
Harvesting into a tank
The flood-and-pour method. Add water to the cup until it rises above the charcoal; springtails float. Swirl gently, then tip the cup and pour the water, springtails and all, into a corner of the tank. Tap the cup to get the ones clinging to the sides. In a new tank, do this once and you are done; they spread through the whole substrate in a couple of weeks. For a mold outbreak, pour them straight onto the mold. Keep the culture out of your isopod tubs as a general rule so what you sell later, if you ever sell, is a pure culture and not a mixed one.
Temperature and light
Room temperature. Ours sit at 68 to 72°F on a shelf in a dark room and breed fine; warmer to about 75 speeds them up. No light needed; they eat mold, not plants. Keep the cup out of direct sun, because a closed cup in a sunny window cooks in an afternoon.
Springtails in the tank versus in the cup
In a bioactive terrarium they need nothing from you at all. Mold shows up, they eat it, they breed in the leaf litter, and you mostly notice them as a few white specks on a rotting leaf. Their numbers in a tank rise and fall with the mold; a tank with no visible springtails is usually a tank with no mold for them to eat, not a dead population. In our display tank they helped finish off a fungus gnat outbreak this month once the sticky trap had knocked the adults down; that story is in how we got rid of fungus gnats. If you do not have a culture yet, ours will be among the first live things we sell; the waitlist is here.
Questions people ask
What do springtails eat? Mold, fungus, and decaying plant film. In a culture, feed them a few grains of uncooked rice or a pinch of yeast and let it mold.
How often do you feed a springtail culture? When the last grains are gone or mushy, usually every one to two weeks. A few grains at a time.
Why is there mold in my springtail culture? Because it is working. Fuzzy rice grains are the food. Sour smell or cloudy water is the problem sign, not mold.
Do springtails need to be split? No. A culture self-regulates. Start a second cup only to have more supply.
Can springtails escape the culture? They jump, but they die fast in dry air, so a cup on a shelf is not a house infestation waiting to happen.