How to Culture Microworms For Fish Fry


How to Culture Microworms for Fish Fry

Because of their attractive movements, live foods can be very useful in breeding fish. They encourage babies to eat more and grow faster. 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. Instead, you can easily start a culture of micro, banana, or walter worms to keep the babies happy and healthy.

What Are Microworms?

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):

– Banana worms (Panagrellus nepenthicola) – Walter worms (Panagrellus silusioides) – Micro worms (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.) When they reach maturity, female roundworms are usually 3-4 days old. They can produce 300 to 1000 live young each year, depending on which species.

Close-up view of starter cultures for micro worms and banana worms

How to Start a Micro Worm Culture

Banana, walter, and micro worms are almost identical in their care requirements, so the rest of the article refers to all three types of roundworms generically as “microworms.” Do not use the following instructions for grindal or white worms, which are annelid worms and need a different kind of setup.

1. Gather the following materials:

– 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. Add a 0.5-inch (1.5 cm) layer of mashed potato flakes to cover the bottom of the plastic container. Keep adding a little bit of water and stirring the mixture until you get the consistency of light and fluffy mashed potatoes. The mixture should not be too dry and crumbly nor wet and soupy.

Note: In our experience, adding yeast does not seem to help or hinder the growth of the culture. We prefer instant mashed potatoes and baby cereal over other options because they don’t have the same smelly odor as oatmeal or other mediums.

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

1. You can make a small opening (approximately 1cm x 1cm) in the middle of the lid with a razor blade, hole puncher or hole saw. This will allow the roundworms to breathe. Cover the hole by taping on a small patch of fabric or stuffing it with a wad of filter floss. This will prevent flies and other pests entering the container. Cover the container.

Notice: When you’re making a large worm culture, it is better to wrap the entire tray in a blanket than cover the holes in its lid.

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. Repeat Steps 2-5 to create multiple microworm cultures, just in case one of the cultures crashes. 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 worms will climb out of the middle and onto the walls. This makes it easy to collect them. Simply use your fingertip, a cotton swab, or a cheap children’s paintbrush to wipe along 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 discovered that microworms fed alone can lead to deformities in fish, whether from nutrient deficiencies and water quality issues. So make sure to add high-quality food like Hikari First Bites, Easy Fry, and Small Fish Food to your fish’s diet.

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. Repeat Steps 2-5 above to create a new cultural unit. Add one spoonful of worms to the existing culture. Once the fry are large enough, we highly recommend switching over to live baby brine shrimp because of high protein, fat, and nutrition content. Find out how to make your own brine shrimp by reading the article linked below.