Blackworms (Lumbriculus variegatus) are the richest live food most of us can keep, and the culture is just a shallow tray of water on a shelf. Ignore the fridge advice you will read from overseas lab suppliers — that is for storing worms still. Growing them happens at room temperature; the thing that kills blackworms in South Africa is a hot summer room, not a cool one.
Photo: Coughdrop12, Wikimedia Commons, CC BY-SA 4.0
The worms live half-buried, tails waving in the current to breathe — that waving is also what makes fish hunt them so eagerly. Keep the tray out of direct sun, in the coolest room you have.
Culture at ±20–24 °C. Production actually improves as the water warms toward that range — but never let it sit above 25 °C, and sustained heat over ±27 °C will kill a culture. On hot summer days, float a frozen water bottle in the tray and move it to the coolest room in the house.
A fridge is only for holding worms you are about to feed, to keep them still and slow. Worms being grown out belong on the shelf.
Feed little: a sinking pellet or a small piece of blanched spinach, only as fast as it disappears. Overfeeding rots the water and is the fastest way to crash a tray.
Change most of the water every 1–2 weeks — sooner the moment it clouds — using same-temperature dechlorinated water, and refresh the paper as it disintegrates. To harvest, swirl the substrate, let the worms ball up, and lift them out with a pipette or small net. Rinse before feeding.
As with every culture on this site: once the tray is producing, split it. A second tray is your insurance against a hot weekend or a fouled water change.
Prefer to see it before you try it? These third-party videos walk through the same culture, step by step. (Overseas setups may differ slightly — follow the advice on this page for our cultures and conditions.)
Lumbriculus variegatus
A meaty aquatic worm that adult fish go mad for — currently out of stock
R350 · 50 worms