Infusoria: the first food for fry and how to use it

Newly hatched fry of many fish are so small that they cannot swallow even fine food. For the first days they need food the size of a speck of dust, and it has to be alive. That is what infusoria are.

What infusoria are

Aquarium keepers use the word infusoria for single-celled organisms that live in water, mostly slipper animalcules (Paramecium). They swim in the water column, and the fry catch them themselves. Infusoria don't foul the water the way dry food does: whatever is not eaten stays alive.

Who needs them

• small fry in their first 5–7 days: gouramis, bettas, many characins and cichlids;
• fry that do not yet take brine shrimp nauplii and microworms;
• crustaceans and larvae that need very fine live food.

Baby shrimp don't need infusoria: young shrimp eat the same as the adults, plus biofilm.

How to grow infusoria from a culture

• take a 1–3 litre jar and fill it with aged tank water;
• add food for the infusoria: a blanched lettuce leaf or a piece of dried banana peel;
• pour in the culture and put the jar in a bright, warm spot, out of direct sunlight, at room temperature;
• after 3–5 days the water turns slightly cloudy, which means the infusoria have multiplied.

Keeping the culture going is easy: once a week pour part of the water into a new jar with fresh food. That way you always have a supply.

How to feed fry

Draw up water with infusoria in a pipette and release it near the fry several times a day. After 5–7 days, when the fry have grown, move them on to microworms and brine shrimp (Artemia) nauplii.

We ship a live infusoria culture together with other live foods: microworms, vinegar eels, tubifex and Artemia eggs.