Microworms are a useful live fish food for both adults and fry. They are a small white nematode worm found naturally in composting plant material and organic soil.

Microworms should not be confused with white worms which are similar but significantly larger. Both worm varieties can be easily cultured for home aquarium use.

I have fed microworms to my corydorus, bristlenose catfish, mountain minnows, and cichlids in combination with other foods. They are great for feeding to baby Siamese fighter fish after they have moved on from first stage food such as paramecium. Ideal for many other fish fry.


Although not as nutritious as brine shrimp, microworms are advantageous in other ways. Unlike brine shrimp, microworms will not swim away from the fry. Instead they sit on the tank floor where clumsy new born fry can snack on them with ease.


Microworms are less expensive than brine shrimp as the population is self sustaining. Unlike brine shrimp no eggs are required to start a fresh batch. The only ongoing cost for the fish keeper is the food required to sustain the microworms.


How To Culture Microworms

The essential parts required:

  • ·   Yeast to feed the microworms. Yeast may become self sustaining where cereal is used as the living medium for the microworms.

  • ·    Vessel for the microworms to be kept in. Should have a lid to promote humidity but small amount of ventilation is required.

  • ·    Medium for the microworms to live upon. This is generally moist cereal or potting mix.

With a cereal based culture the yeast will feed on the carbohydrates and in turn become food for the microworms. Dry yeast can supplement the microworms diet. In a soil based culture the yeast cannot sustain itself and will need to be added at regular intervals.


Commercial cultures from aquarium businesses are almost exclusively cereal based. A culture will remain productive for a number of weeks but will need to be freshly restarted after worm numbers have peaked.


To make a fresh microworm culture:


  • ·   Select some cereal based food such as stale white bread or porridge. Baby cereal and wheat biscuit style cereals are excellent. Corn flakes seem less useful.

  • ·    Boil or microwave this mixture, place it in a Chinese container or similar. Allow it to cool then place some holes in the lid. Ideally the mixture could be autoclaved. This step reduces the number of mould spores that have the potential to take hold and destroy a microworm culture. A mature culture will out compete mould but freshly started cultures are vulnerable.

  • ·   The consistency of the cereal should be moist but not wet. Although these worms will stay alive for many hours on the bottom of the aquarium, a microworm culture can drown in only a few millimeters of water.

  • ·    Collect as many worms as possible and smear them over the top of the medium. Microworms only live on the surface where they can readily breathe. Sprinkle with dried yeast.

Harvesting Microworms

Worms can be harvested
from a new culture in a week if the growing environment is warm and conditions are favourable. In cooler surroundings they will not die but will stop breeding.

As the container becomes over populated the microworms will climb up the walls and form a thick coating. You can wipe them off with your finger or a small spatula to feed to your fish.

When the culture is past it's peak or the microworms are not as productive due to temperature, harvesting the microworms is not quite as straight forward. Although countless worms may be visible shimmering on the surface, cereal and yeast will also be collected if the worms are scraped off. The yeast and cereal will foul the water when added, but a solution is available.

  • ·   Cover the surface of the culture with paper towel.

  • ·    Wait at least half an hour until the paper has become wet and microworms have burrowed through the towel to the surface.

  • ·    Microworms can now be scraped gently from the surface of the paper towel.

If you let your microworm population increase until they need to be housed in a fish tank or other large container you will be able to harvest and freeze the excess for leaner times.

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