How to Culture Microworms For Fish Fry


How to Culture Microworms for Fish Fry

The attraction of live foods is a great way to breed fish. It encourages the babies’ growth and eating habits. However, some fish (such as betta fish, ram cichlids, and rainbowfish) produce miniscule offspring that are too small to eat traditional fry foods like live baby brine shrimp or crushed flakes. To keep your babies happy and healthy, you can start a micro, banana, or even walter worm culture.

What are Microworms and How Can They Help?

Microworms are nematodes or roundworms found in the Panagrellus Genus. The most popular types used in the aquarium hobby are (in order of smallest to largest):

– Panagrellus nepenthicola – Walter worms – Panagrellus silusioides – Microworms – Panagrellus Redivivus

They can be as small as 1-3mm in length, and 50-100 microns wide. This is slightly larger than vinegar eels. (By comparison, newly hatched brine shrimp are 450 microns in size, so even the tiniest fry can slurp down nematodes like noodles.) The maturity age of female roundworms is 3-4 days. They can produce 300-1000 young per year depending on their species.

Close-up of micro worm starter cultures versus banana worm starter cultures

How to Start a Micro Worm Culture

Micro, walter, banana and micro worms have almost identical care requirements. The rest of this article refers to them all as “microworms” and not the grindal or white roundworms. They require a different setup.

1. The following materials are required:

– Starter culture of banana, micro, or walter worms (purchased from a fish club auction, local fish store,, or other online source) – Box of plain instant mashed potatoes (without any extra flavoring) – Several small plastic tubs or deli containers, about 5 inches (13 cm) in diameter or larger, with taller sides and tight-fitting lids – Dechlorinated water at room temperature

1. To cover the bottom of your plastic container, add a layer of mashed potato chips measuring 0.5 inches (1.5 cm). Keep adding a little bit of water and stirring the mixture until you get the consistency of light and fluffy mashed potatoes. The mixture shouldn’t be too dry or crumbly, nor too wet and soupy.

Note: Adding yeast to the culture does not seem either to aid or hinder its growth. Also, we prefer to use instant mashed potatoes or baby cereal because they don’t produce a smelly odor like oatmeal and some other mediums do.

1. After the mixture has been incorporated into a container, spread it out evenly. Then add a tablespoon of starter worm cultures. Place the worms on the medium.

1. Use a razor blade to cut a small hole in the lid (approximately 0.5 cm x 1.0 cm) so the roundworms can breathe. Tape or stuff the hole with a piece of filter floss. This will prevent flies and other pests entering the container. Cover the container.

Notice: Some people prefer to cover all of the holes in the lid with a pillowcase, even if they are making a bigger worm culture.

1. Label the culture with the type of roundworm you’re using, as well as the date it was created because the cultures have an expiration date (see below). The container can be kept at room temperature. 2. For the event that one of your cultures fails, you can repeat steps 2-5. The medium may become spoiled, moldy, infested by bugs, or filled with worm waste, so it helps to have some backups to work with.

How to Harvest Microworms to Feed Fish

Some of the worms will start climbing out of the medium and up onto the walls, making it easy for you to collect them. Use your fingertip, cotton swab or a cheap child’s paintbrush to clean the sides of the plastic tub. Dunk the worms directly into the tank to feed the fish. The microworms will live between 8 and 12 hours in water. Avoid overfeeding to prevent water quality problems. It’s okay if a little potato mixture gets into the aquarium because the omnivore fish will eat it along with the roundworms.

Hobbyists have learned that only feeding microworms can sometimes lead to deformities, either from nutrient deficiencies or water quality issues, so make sure to supplement your fish’s diet with other high-quality foods like Hikari First Bites and Easy Fry and Small Fish Food.

How to maintain the micro worm culture

Over time, the culture becomes more and more filled with worm poop, making the medium very runny in consistency. Make a new culture by repeating Steps 2-5 from the above section and adding one spoonful of worms from the old culture. Because of the high nutrition, protein, and fat content, we recommend switching to live baby brine shrimp when the fry reach sufficient size. Find out how to make your own brine shrimp by reading the article linked below.