Grindal Worms Info

Gills and Fins – your source for live grindal worm cultures and information.


Origin:  Grindal worms grow wild in our soil like their slightly larger cousins the white worms.  Mrs. Morton Grindal of Sweden extracted these smaller worms from her white worm cultures and made her name famous in fish keeping circles around the world.  Starter cultures are now readily available from our store. 

Breeding:  Both participants in the process swapping sperm. Grindal worms carry both male and female parts. They lay eggs in the soil which hatch and grow rapidly. Make sure to use your Culture soil as it will be full of eggs.

Temperature:  Grindal worms do best at room temperature.  You can keep them right next to your fish tank.  How convenient is that!!

Storage:  You need to cover your cultures to keep out invaders that eat the same food:  fruit flies, mites, and springtails.  You also want to keep out larger critters that will eat your Grindal worms: ants and mice. You can use Rubbermaid sandwich containers or if you need large amounts of worms a larger container with a lid.

Grindal worm culture
Everything needed to Culture Grindal worms

Size:  Adult Grindal worms max out at about ½ inch. 

Sorting:  Put your worms in a water-filled container and swirl the water in a circle.  The larger worms settle to the bottom first, you can then pour the smaller worms into another container and feed the larger worms to your fish, such as bettas, killifish, guppies, tetras, barbs, angels and other community fish.  Catfishes, especially corydoras love any size Grindal worms.  Picky eaters like glassfish and spiny eels slurp them eagerly.  All livebearers love Grindal worms.

Foods:  Grindal worms will eat a variety of foods of grain origin.  Some worm wranglers feed them table scraps (treating them like compost worms).  Grain-based products work better:  baby cereal, instant oatmeal, cornmeal, bread, fish food or dog/cat food.  We use Dog food because it’s full of vitamins the preservatives in it keep it from molding for a long time. Some hobbyists prefer to feed their worms fish food, figuring that a gut load of fish food will most likely meet their fishes nutrition needs best. 

Grindal Worms
Grindal Worms

Culture Media:  You can culture your Grindal worms in potting soil with a little peat moss mixed into lighten its texture.  Aim for a damp but not wet culture medium. We do not use coconut fiber because the worms don’t like it. There have been studies done where half of a culture is soil and the other half is coconut fiber. All the worms stayed on the soil side. Use what works best for you, but we use a high-quality topsoil with added peat moss and organic matter. Our cultures grow like crazy.

Grindal Worm Media
Potting Soil we use on our cultures.

Feeding:  Feed small amounts that your worms consume daily.  Add more food as your culture increases and overfeeding will encourages the growth of mold, so if you get pieces that mold just remove them and replace with new pieces. We used dog food because it strongly resists mold and you can scatter pieces where the worms are. Once your worm herd gets going, harvest your worms daily or at least every other day or they will overpopulate your container. They multiply very rapidly, so a new culture will come populate in a couple weeks. If they start crawling up the sides, they are overpopulated or too wet. If overpopulated, start another culture. If too wet, add more dry media or make a larger hole to let them dry out a bit.

 Harvesting: Lay a sheet of glass or plastic needlepoint (we prefer needlepoint) on their food. As the Grindal worms cluster around the food, many will stick to the cover sheet. Lift it up and rinse your tasty worms off and feed to your small to medium fishes.

Grindal Worms on Needlepoint

Get your Grindal worm culture at our shop by clicking here and check out the DIY Cultures section for more on setting up your Culture.