How to culture grindal worms

Grindal worms (Enchytraeus buchholzi) fill the gap between microworms and adult food: a meaty, mixed-size worm for growing fry, killifish and conditioning adults — cultured in a lidded box on a shelf, no fridge required.

The culture box

• Shallow lidded box with a few ventilation holes
• 2–5 cm of damp coconut coir, peat/soil mix, or an open-pore sponge
• A small glass or acrylic plate for feeding and harvesting
• Food: oats, fish food or softened dry pet food

The medium must be damp, never sodden — waterlogged, airless media is what makes cultures smell and crash.

Feeding and harvesting

Sprinkle a pinch of food on the medium and cover it with the glass plate. Worms gather under the plate to feed, so a day later you can simply rinse the plate into a container of clean water and pour off clean, medium-free worms.

Feed only what disappears in 24–48 hours. Leftover food is the number one cause of mites, mould and crashed boxes. If food remains, remove it and feed less.

Keeping production up

Keep the box on a cooler shelf at room temperature, away from heat and direct sun. When production drops after some months, split the culture into fresh medium — take a spoon of old medium (it carries eggs and young worms) into each new box.

A single harvest holds worms from ±1 mm to ±10 mm, so one box feeds fry and adults at the same time.

Video guides: watch it done

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.)