First of all, it should be noted that microworms aren't something that everyone wants to keep or even every fish keeper wants to keep. Microworms are a tiny nematode and not actually a worm at all. In nature they are commonly found in rotting food such as fruits and vegetables or wet grains. They are very small at just over 1mm in length. However, they are easy to culture and easy to feed to small fish and fry.  


The Life Cycle of Microworms

The microworms grow in warm temperatures from about 60 degrees Fahrenheit to about 80. Each microworm lives about 20 to 25 days and will start having babies about 3 days into their life. Each day they will have about 40 babies. In this way a small culture of microworms can produce a lot of microworms for food.

Culturing Microworms

Culturing microwrms is really easy to do once you receive a starter culture. This is a small (or large) batch of microwomrs from an existing culture. You can actually culture microworms with as little as a ½ tablespoon of old culture mix as long as it was a healthy culture. Here's how you do it.

  • Choose a Container. You can choose a very small plastic container or a larger one. Mine are kept in plastic shoe boxes, but something like a butter dish or even a small plastic condiment cup works. You will want to punch a few holes in the top and it can help to cover them with a cloth or coffee filter to help prevent the worms from escaping. The air will help keep the microworms in the container, will make sure they don't suffocate, and will help you to have a healthy culture.
  • Mix the Medium. Some people call this a base, a medium, a media, or even bedding. Whatever you call it, you will want to mix up and have it ready for your microworms. The worms will live in the bedding and eat it (and poop in it and so forth). The medium can be made from a lot of different types of food. Most common is oatmeal. Use instant oatmeal and mix it with water until it is smooth and soft, but not runny (the microworms can drown in standing water). Other choices can include instant mashed potatoes, corn meal, porridge, baby cereal, bread, and dry cereal. In any case, you want that smooth texture that is not thick and not runny. You may have to cook some foods in order to get them soft and smooth (such as cornmeal). You can also mix more than one food together. Most people tend to find a preference after experimenting with it for awhile. (My current preference is 1 part cornmeal to 3 parts instant oatmeal covered with water and letting it sit for about 3 hours). Place about ½ inch of the medium on the bottom of the containers.
  • To Yeast or Not To Yeast. Some people swear by yeast in the culture and claim that this is the only thing in the culture that the microworms eat. However, that isn't true. They will happily live in the culture medium without any “food” added to it. Or you can choose to add yeast. The advantages is that it keeps the culture smelling acceptable longer, it does increase how fast the culture blooms, and it can keep it from souring. The disadvantages are that the yeast gives of carbon dioxide that that in turn can blow the lid off if you don't have adequate ventilation, can suffocate the worms, and can lead to a bubbling mess. By adding just a tiny bit of yeast to the culture you can prevent a lot of these problems. To add just a little bit at a time you will want to put them in a jar with a sprinkle top like a salt shaker or a spice container. If you are going to add yeast then you will want to do that now. Remember, just a sprinkle.
  • Add the Microworms. Now you will want to add the microworms. To do this you will sprinkle the culture across the top of the new medium. It doesn't take very much so don't worry if your culture is small.

Harvesting the Microworms

You will want to harvest the microworms so that you can feed your fish. You don't want any of the culture medium to end up in the aquarium because it can make your water go bad and add to the ammonia and nitrites of the water. There are a couple of different options for harvesting microworms.

  • Scrape the Edges. The most common method for harvesting microworms is to scrape the sides of the container. The microworms will climb out of the medium and onto the sides leaving behind the yuckies. You will take a cotton swab, a popsicle stick, a tooth pick, or even your finger and then swish it into a small dish or cup of water. You can then add the microworm water to your fish tank. A clear glass will allow you to hold the water up to the light and see how many microworms are in the water and decide how much water to add to each tank. If feeding them to fry you don't want to add a lot of them at one time because they might not all get eaten and then they will die and dirty the water.
  • Paper Towel It. If you need a lot of microworms at one time then it won't do to scrape them off the sides. To get worms this way you can take a piece of paper towel and get it wet. Gently place the paper towel over the culture. The microworms will climb through the paper towel leaving the medium behind. You will then want to use a spoon to collect the worms off of the paper towel. You can then add one or two drops to your tank or mix this with water the same as you did before.

Reculturing Microworms

You will want to check your culture every day or so. You want to add some dry oatmeal to the mix if it gets watery. If it gets dry you should mix some fresh medium and add that to the top. Every three weeks or so you should start a new culture. To do this you simply take some of the old culture and set it aside and follow the direction to make a new culture. Sprinkle your old culture on the top.

Obtaining Microworms

Microworms can often be obtained from friends, other fish keepers, and aquarium clubs. For those who don't have these resources you can buy them on AquaBid, eBay, or even at my site The Freshwater Reef. The microworms will travel in the mail and arrive ready for culturing.

Microworms are great live fish food for small fishes and fry. They are easy to keep, inexpensive, and sometimes even a little fun. They are even a great science experiment for little kids. If you take care of them regularly then you will be able to have them for years from one small investment and you will be able to raise more and healthier fish because of it!