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Grindal Worms

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How To Culture Grindal Worms









Grindal Worm Factoids
Origin Extracted from white worm cultures
Sex Info Each worm contains male and female equipment
Temperature Room temp best
Size Adults 1/2 inch max. Most smaller.
Biggest Pests Fruit flies, mites, and springtails
Likely Predators Ants and mice
Biggest Threats Too much water. Too little water.
Culture Medium Potting soil, peat moss, or coconut fiber
Foods Foods of grain origin
Breeding Comments Reproduces incredibly fast. Feed out daily.

Origins: 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 a variety of sources. I got mine from Howard Broderson, one of our local betta suppliers from Hampton. Or you can look under rocks in your back yard and maybe get lucky.

Sex Stuff: If you’ve ever hunted nightcrawlers, you know how these smaller cousins breed. Both participants in the process lay eggs which hatch and grow rapidly.

Temperature: Unlike their larger cousins, nightcrawlers (45 F) and white worms (55 F), Grindal worms do best at room temperature. You can keep them right next to your fish tank if you desire. And you can feed them the same food you feed your fishes if you prefer.

Keep Covered: 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.

Aeration: You will need to let air into your culture or your worms will suffocate or drown in their own waste products. Punching multiple pinholes in your container’s side should do the trick – holes too large will enable fruit fly invasions. The pinholes we punched in the Rubbermaid containers “healed” faster than a vampire’s wound. So we cut holes in the tops and pulled filter floss into them to keep out invaders.

Size: Adult Grindal worms max out at about ½ inch. Most of your harvest will consist of smaller worms. You can easily sort them by size if you prefer. Size makes little difference to most hungry fishes.

Sorting by Size: Put a glob of worms in a water-filled pint jar and swirl the water in a circle. The larger worms settle to the bottom first. You can pour the smaller worms into another container. Feed the larger worms to your larger fishes (actually larger small fishes) such as bettas, killifish, guppies, tetras, barbs, angels and other community fish. Catfishes — especially corydoras — love any size 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, and bread. White bread works best because the preservatives in it keep it from molding for a long time. The Iron Kids crust-less bread works great. Other 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. We tried chicken food because we have a 50 pound sack of it. We prefer white bread moistened with tap water. Remove the crust. Treat them like an eight-year-old kid.



Housing: Our local dollar store has Rubbermaid sandwich containers at two for a dollar. These have nice tight lids and work well. They are just the right depth for Grindal worms.






Culture Medium: You can culture your Grindalworms in potting soil or good old Iowa dirt with a little peat moss mixed in to lighten its texture. Some keepers use peat moss with added lime to decrease the acidity. This is the hardest row to hoe. Peat moss takes forever and a half to waterlog. Coconut fiber soaks up water in about an hour. Potting soil makes mud instantly. Aim for a damp but not wet culture medium.



Feeding Technique: Feed small amounts that your worms consume daily. Add more food as your worm herd increases. Over feeding encourages the growth of mold. We used white bread because it strongly resists mold. Whole wheat gets moldy fast.

Feeding Schedule: 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. A new culture will come “on-line” 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 take their lid off to let them dry out a bit.

Harvesting Technique: Lay a sheet of glass or plastic atop their food. As the Grindal worms cluster around the food, many will adhere to the cover sheet. Lift it up and scoop your tasty worms off with your finger. Feed to your small to medium fishes. the second method is to lay a piece of the dirt on a plastic matte in a shot glass filled with tank water. After a few minutes the worms will fall to the bottom and you can suck them up and squirt into your tanks.



One of the new ways to breed Grindal worms is on green scrub pads with wet cat food. Seems to work very good and make collecting very easy. The one issue is that the worms seem to grow a little to fast and we end up culling some worms to keep the culture from crashing. If you need a lot of worms fast this is the best way. 



Last Word: Do not feed Grindal worms exclusively. Vary your fishes diet. And wash your hands after playing in the dirt.


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