How to culture daphnia (moina) at home

A note on names first: the “daphnia” sold in South Africa — including ours — is usually moina, a smaller, warm-water cousin of true Daphnia. This guide cultures it as moina: warmer water and faster reproduction than the overseas Daphnia magna guides describe. A moina culture turns one starter portion into months of live food. The whole system is a tub of greenish water — the craft is in feeding little enough that the water stays alive, and in never trusting a single culture.

What you need

• A 10–20 L tub, bucket or old tank
• Aged or dechlorinated water (old tank water works well)
• Gentle aeration, or a still-water spot with indirect light
• Food: green water, active yeast solution or spirulina powder
• A fine fish net or turkey baster for harvesting

Starting the culture

Fill the tub with aged water at 20–30 °C (fastest reproduction at 24–28 °C) and add the starter culture. Give it a day or two to settle before feeding. Indirect light keeps algae growing gently in the water, which is free food working for you around the clock. In winter, a cold tub is the usual reason a moina culture “mysteriously” slows down.

Feed only when the water starts to clear — a faint haze means food is present. The most common way beginners kill moina is overfeeding: uneaten food crashes the water, not hunger.

Harvesting and feeding fish

Scoop with a fine net or baster, rinse briefly if you like, and feed what your fish finish in a few minutes. Uneaten moina keep living in freshwater until they are eaten, which makes them one of the safest live foods to feed generously.

At ±0.4–1.5 mm, moina are far smaller than true daphnia: newborns suit larger fry and the adults suit small fish. Tiny fry should still start on microworms, banana worms or vinegar eels and graduate to moina as they grow.

The golden rule: two cultures, always

Moina cultures boom and crash faster than true daphnia — that speed is their strength and their risk. Splitting your culture into two tubs costs one bucket and five minutes, and it is the difference between a minor hiccup and having no live food for a spawn. Rest a crashed tub, refill with aged water, and reseed from the survivor.

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.)