How to Culture Grindal Worms

Grindal worms (Enchytraeus bucholzi) are small, white worms that make excellent food for various sizes of fish and amphibians. They can be purchased from, and can also be obtained from aquarium hobbyists.

Supplies for culturing Grindal worms

A medium to large plastic food saver container with a tight-fitting lid makes an excellent culture container:

For ventilation, I drill a few holes in the lid, (2-4 1/8” holes are sufficient) and then stuff them with pieces of filter floss. This prevents pests from entering the culture.

For substrate, potting soil, compost, and so on can be used, I have always used ground coconut fiber, also called coir fiber, and sold under many brand names. It comes in dried, compressed bricks like this:

Place the brick in a large plastic bin, and add between 1/2nand 1 gallon of water. The brick softens, darkens, and expands as it absorbs water. One brick makes enough substrate for several cultures. When it is uniformly damp, but not soaked, it is ready to be used as substrate for your Grindal worms. If you squeeze a small handful and it feels damp, perhaps with a couple of drops of water dipping out, it is about right. If you squeeze it and a small stream of water runs out, it is probably a little too wet.

Depending on the size of the container you choose, add about 3 inches of substrate to the container.

Next, a you’ll need a flat piece of plastic or glass that covers most of the substrate surface. This will serve as a feeding station for the worms, as well as a harvesting aid. You can cut a lid from a disposable plastic food container (such as a yogurt lid or the thin, clear boxes that salad greens come in) or you can use a sheet of needlepoint canvas:

Now the culture is ready for you to add the starter culture of worms and some food to get them started.

Feeding Grindal Worms

Grindal worms are really not very picky about what they eat. It is important, however, to provide the, with nutritious food that will pass on to your pets. It is also important to avoid foods that tend to encourage pests. I have had the best results with high-quality, grain-free dog kibble. I store it in the refrigerator to keep pests such as mites out of it:

You can also use kitten food, fish flakes or pellets, cooked oatmeal, soft vegetables such as zucchini, or bread soaked in milk. I tend to avoid dry, grain-based products, such as inexpensive dog food, as they may introduce pests such as grain mites.

Place the food under the piece of plastic or glass. Grindal worms prefer moist food, so mist the food lightly before covering it again. Grindal worms seem to thrive and breed best when they are fed enough so that the food is nearly, but not quite gone, twenty-four hours later. If there is a lot of food left, or none at all, adjust accordingly. The culture will grow quickly, so the quantity you need to feed will change as the culture grows.

Within a week or two of starting your culture, you will have many more workpms than you began with, and you can start to harvest worms. Lots of worms will congregate on the underside of the plastic or glass substrate cover, especially near the food. You can use a cotton swab to gently scrape some of the worms off into a small container of water. The worms will sink to the bottom. Bits of substrate and worm food may come along with them. Swirl the container of water, and pour off the dirty water, being careful to retain the worms. Repeat this process a few times to remove most of the contaminants. You’ll have clean worms at the bottom of the container, read to feed to your fish or amphibians.

Pests in Grindal Worm Cultures

Some of the most common pests that can show up in Grindal worm cultures are grain mites, fungus gnats, and phorid flies. In the past, I have purchased cultures online, only to find them contaminated with one or more of these pests. It’s a pretty common issue. I have found that the best way to eliminate these pests is to start a completely new copultire with fresh, clean coco fiber. I sometimes even microwave and cool the freshly hydrated coco fiber just before using it to make sure the substrate is clean. I use the water-swirling technique described above to separate the worms from any mites or fly larvae, and start a new culture. I am careful to make sure the ventilation is pestproof, and make sure not to feed pest-contaminated foods. This method has worked very well for me.

For more information on culturing Grindal Worms, check out my ebook:

I am a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to In other words, I earn a small commission  when you use that affiliate link, at no cost to you.