Keeping cultures alive in winter (and through loadshedding)

South African culture-keeping has two seasons the overseas guides never mention: winter, when an unheated room in the Cape or on the Highveld stalls every warm-water culture you own, and loadshedding, when the air pump that your blackworm tray depends on stops being a guarantee. Neither has to cost you a culture. Here is how to winter-proof the shelf, culture by culture.

Know each culture’s cold limit

• Daphnia (moina): stalls below ±20 °C, fastest at 24–28 °C. Winter job one is warmth — move tubs to the warmest room, against an internal wall, off a cold floor.
• Microworms, banana worms, vinegar eels (all on oats): the winter-proof cultures. Room temperature and below is fine; they slow but survive, and a tub in a cupboard near a water heater barely notices July.
• Grindal worms: prefer it cool — winter is their season. The shelf that was too warm in January is perfect in June.
• Blackworms: cool-water animals (keep below 25 °C, ideally 20–24 °C) — winter suits them too, provided the tray never actually approaches freezing outdoors.

Cheap warmth for the moina tubs

Insulate before you heat: a tub inside a polystyrene box (the fish-shipping box your last order arrived in) holds temperature through the night better than a naked bucket in a warm room. Stand tubs on wood or foam, never straight on a tile or concrete floor, which is a heat sink with a grudge. If you do heat one tub, heat the backup — a small aquarium heater in the reserve culture is insurance for the whole shelf, because the reserve is what restarts everything else.

Loadshedding: design for the power you actually have

Audit honestly: worm and eel tubs need no electricity at all, which is why an oats-based shelf survives any schedule Eskom invents. Daphnia (moina) tubs do fine without aeration at moderate densities — lower the density before winter rather than relying on a pump. The genuinely pump-dependent setup is the blackworm tray: run it on a battery air pump (the USB/battery pumps sold for loadshedding cost less than one blackworm portion), spread worms thinner, and change water more often during heavy outage weeks. And keep the habit that beats all gadgets: two of every culture, in different spots, so no single cold snap, outage or fouled tub can take the whole menu.