Culturing Microworms/Walterworms/Banana Worms as a Live Food

Microworms, Walterworms, and Banana Worms are all tiny nematode works that can be cultured in precisely the same way. They make a good food for aquarium fish fry, as well as other small fish.

Supplies for culturing microworms

Starter cultures for Microworms can be purchased from, or you may be able to obtain them from local aquarium hobbyists. I always have starter cultures available. Contact me about obtaining one.

Supplies for Culturing Microworms

You will need a culture container. I often repurpose large yogurt or cottage cheese containers. You can also use a food saver container like these:

Many different plastic containers will suffice. The most important consideration is a tight-fitting lid that can be punctured with a pin or similar instrument. A pin is ideal, as the small holes will help keep pests like fruit flies from entering the culture. Make about 15-20 pinholes. Alternatively, you can cut or drill one or two large holes and plug them lightly with aquarium filter floss.

Next, you will need a culture medium. Corn meal, oatmeal, moistened bread, semolina, and other media can be used. I prefer old-fashioned rolled oats, cooked according to the directions on the package, but without salt. once they are cooked, they can be used plain, but I prefer to add some additional ingredients to increase the nutrients passed on to my fish.

For each cup of cooked medium I add roughly a teaspoon of the following:

You can also add a pinch of active dry yeast. This is optional, as the starter culture of worms will contain some live yeast as well, but it may speed up the development of the culture slightly, and will do no harm.

Next, once the medium has cooled to room temperature, spread the starter culture in a thin layer over the top of the medium. Cover the culture, set it aside, preferably in a warm (75-80 F) place, and wait a few days. Soon, if your culture is viable, when you shine a light onto the surface of the culture, you will notice a shimmering effect. This indicates that the culture is teeming with microworms. A few days later, the worms will have reproduced so much that they will be climbing the walls of the container in droves.

Harvesting Microworms

A cotton swab or wooden ice cream stick, or even your finger if you’re not squeamish, can be used to scoop a portion of worms from the sides of the container.

Simply swish the cotton swab or other collecting implement into the aquarium water. Newly born livebearers, free-swimming cichlids fry, and nearly any fish fry past the Infusoria stage will eat microworms. Keep in mind that good water circulation will keep them floating for a short time, but they will eventually sink, and will,do so quickly in still water. This makes them a great food for fry that feed preferentially from the bottom.

Microworm Culture Maintenance

Besides regularly feeding from the culture, there are two regular maintenance tasks to keep your cultures producing.

One is to keep the ventilation at the right levels. Too much ventilation will inhibit the worms from crawling up the sides, making harvest difficult. Too little ventilation, and the worm culture can die off. Over time, worms crawl up to the ventilation holes, leaving a residue that can cake over the holes, reducing the ventilation. Plastic also tends to self-heal to some extent, reducing the size of the holes. Occasionally you will need to rinse the lid thoroughly in hot water to remove the residue, and/or create some new holes. If you use a larger hole plugged with filter floss, replace the filter floss occasionally.

The second regular maintenance task is to start a new culture every week or two. Keep two or three cultures going at all times. You can discard the contents of the oldest culture, rinse it out, and add new medium. Use about a tablespoonful of medium from your producing culture to seed the new culture, and add a tablespoonful of new medium to the producing culture to extend production. In this way you can ensure a constant supply of Microworms for your fry.

I made this video back in 2011, but the information is still valid.

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