Raising Microworms
Denny Rogers – October 2017
I’ve been raising various live foods suitable for feeding to fish fry continuously for over 25 years. During that time I’ve gone through a learning curve for each of these various foods. I’ve tried many variations for raising each species, and over time I have discovered methods that have consistently work best for me. I’m going to focus on two foods, microworms and vinegar worms, which are probably the easiest for beginners to start raising for fry food.
Microworms
Microworms are a type of nematode worm that are very nutrition for baby fish. There are several species or types (banana worms, Walter worms, etc.) that are very similar, and most cultures are a mix of several different species. For our purposes, we will treat them all the same.
Figure 1 Microworm culture under a microscope
It does seems like every hobbyist has their own favored method of culturing their microworms. Originally I experimented with several different growth medias with very mixed results. My cultures would typically last about a month, but often crashed from contamination by mold and bacteria. Many of the medias also failed to solidify sufficiently which caused problems trying to harvest the worms. When cultures failed, odor could also become a problem. Significant others don’t appreciate a smelly culture in close proximity.
Figure 2 Microworm culture at about two weeks
I finally settled on using instant potato for my media. More specifically, I’ve been using potato buds with great success. Preparing to start a culture is simplicity itself. I use equal parts potato buds and water. Once mixed, the culture will set up in a matter of 20-30 seconds. I’ve been using (and reusing) deli food containers to hold my cultures, but just about any container with a lid will be acceptable.
Figure 3 Microworm Ingredients
Figure 4 Start with potato buds
The ratio of the potato buds and water is not absolutely critical, but should be somewhat equal. Add the water to the potato buds, and swirl the container to get a uniform mix.
Figure 5 Add an equal quantity of water
After the culture has solidified, I add a liberal sprinkling of dried active yeast on top of the media. Originally, I was using the small packets that are often used in bread making. I was not happy with the inconsistent results, and often the yeast would not start growing. Eventually I discovered that you could buy a small jar of yeast that would remain viable for more than a single attempt to start a new culture. Now I use a yeast brick that I’ve been getting at Sam’s club. It’s usually packed in 2 separate packages. I use one, and freeze the other. Between the two packages, it seems to remain viable for several years.
Figure 6 Sprinkle a generous portion of yeast on the media.
Once I’ve got the culture set up with the media and yeast, I take a small sample from an existing culture, and inoculate the new culture. We had Mike Hellweg, author of “Culturing Live Foods” speak at our club several years ago. One of the comments he made was that the microworms that crawl up the sides of the growing container are predominately males. Ever since, I’ve been getting my sample from the top of the media in the existing culture rather than from the sides of the container. It’s best to pick up as little of the media as possible to reduce your chances of contaminating the new culture. A healthy growth of yeast will minimize this risk.
Figure 7 Inoculating from an existing culture
Once a culture is set up and inoculated, you do need to make sure that oxygen can get into the container. Using the plastic containers, once I put the lid on, I poke holes in the lid with a straight pin. This allows for the entry of oxygen into the container, but minimizes contamination by fruit flies. It doesn’t eliminate the possibility completely, but it helps. Fruit fly larvae are a nuisance if they manage to get in your culture, because the larvae do eventually hatch into fruit flies. They don’t cause problems other than hatching and flying around your house or fish room. I’m assuming the females are attracted to the yeast smell, and are able to lay their eggs through the air holes in the lid.
Figure 8 Putting air holes in the container
My cultures are started every week or two to keep an actively growing culture available as well as a backup in case any of my cultures do crash. Originally my cultures had to be replaced every month, but for some reason my cultures now are still active after six or more weeks.
One other advantage to growing microworms for food is the ability to gut load the worms with additional nutrients. I frequently add garlic powder and paprika to my media. Usually this is only half a teaspoon per culture, but I do think it helps. There are also other additives you can add if you feel the need to enrich your culture media.
Figure 9 Enriching the media with paprika or garlic
Harvesting the worms is mostly just a question of how squeamish you are. You can use your finger around the side of the container, or you can use a spatula or other similar kitchen gadgets to scrape the worms out of the container.
While this is my method of choice, I do have to say that many other hobbyists have different method, and are very successful. This method has worked best for me over the 25 years I’ve been raising microworms, but don’t be reluctant to experiment.