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. Instead, you can easily start a culture of micro, banana, or walter worms to keep the babies happy and healthy.

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 sepinthicola (Banana worms) – Walter worms, Panagrellus Silusioides (Walter worms) – Micro worms, Panagrellus redivivus

They range in size from 1-3 mm in length and roughly 50-100 microns in diameter, which is slightly bigger than vinegar eels. (By comparison, brine shrimp that have just been hatched are approximately 450 microns long, so even the smallest fry can eat nematodes as noodles. Female roundworms reach maturity when they are 3-4 days old and can produce 300-1000 live young in their lifetime, depending on the species.

Close-up of banana worm versus micro 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, AquaBid.com, 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 should not be too dry and crumbly nor wet and soupy.

Note: We have found that yeast does not appear to affect the growth of the cultures. 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. Pat down the mixture until it is spread evenly in the container and then add a spoonful of the starter worm culture. Spread the worms out onto the medium.

1. Cut a small hole (approximately 1 cm x 1 cm) in the center of the lid using a razor blade or even a hole puncher so that the roundworms have air to breathe. Cover the hole by taping on a small patch of fabric or stuffing it with a wad of filter floss. This stops flies and other pests from getting into the container. The container should be sealed.

Note: If you are making a larger worm culture in a whole tray, some people put the whole tray in a pillowcase rather than covering all the holes in the lid.

1. You should label the culture with the roundworm type you are using and the date it was made. Cultures have an expiration date (see below). The container can be stored at room temperature. 2. To make multiple microworm cultures, repeat Steps 2-5. You should have backups in case the original medium becomes spoiled, moldy or infested.

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. Simply use your fingertip, a cotton swab, or a cheap children’s paintbrush to wipe along the sides of the plastic tub. To feed the fish, dunk the worms into the tank. The micro worms live approximately 8-12 hours in water, so do not overfeed to avoid water quality issues. It’s okay if a little potato mixture gets into the aquarium because the omnivore fish will eat it along with the roundworms.

Hobbyists know that microworms are sometimes difficult to feed. This could be due to nutrient deficiencies, water quality issues, or a lack of food.

How to maintain the micro worm culture

The culture will become more and more contaminated with worm poop over time. This makes the culture very thin. Make a new culture by repeating Steps 2-5 from the above section and adding one spoonful of worms from the old 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.