Grindal Worms can be cultured exactly as White Worms but are a much more adaptable species and have a greater tolerance for warmer temperatures. Maturity has been reported to occur around 16 days at 20°C, the clitellum forming when the worms are about 3 – 4 mm. The generation period (cocoon to cocoon) is about a month at 20°C.
Grindal Worms require soils containing relatively high organic matter content and a soil pH of about 6.8 to 7.2 for optimal conditions. If the culture is maintained properly, the worms will gather in mass on the surface of the soil. The worms will often congregate on the glass cover where they can be scraped off and fed to fish.
Experience has shown that shallow wooden boxes work best. Typical worm boxes are 1/2 to 2 1/3 inches long, 6 to 12 inches wide and no more than 2 1/2 to 4 inches deep. In any case, the use of several small cultures rather than a large one is advisable.
Grindal Worms reproduce normally at and above 46 ~ 50°F, with optimum growth and reproduction occurring between 59 ~ 70°F. As the temperature begins to rise or fall below this range; their production rate will decline.
The culture must be covered to block out light and keep out predators. Ants, beetles, and other insects will feed either on the worms or the food. A secure lid and careful placement of the culture box will prevent such pests. An inner soil cover is recommended to keep the soil surface from drying out.
Grindal Worms will eat just about anything organic. Apiarists feed their worms vegetable based foods such as plant material, oatmeal, bread soaked in milk, wheat flour, cereal, mashed potato and dozens of other similar foods. They will even eat flake and pelleted fish foods, dry dog and cat food, if they are pre-soaked beforehand.
You will need to inspect the culture for food levels two or three times a week. If the food is gone, then increase the amount of food given. If food remains, then remove the excess and reduce the amount provided.
Grindal Worms should not be fed too heavily at first because surplus food tends to attract mites, fun-gal growth, and bacterial contamination. You will have to regulate the amount of food offered dur-ing the first month until the culture stabilizes.
Spray the surface of the soil with water to maintain a damp, but not soggy, look and feel. A plant sprayer or mister can be used for this purpose. The regulation of moisture may be aided by removing the cover for a time as necessary to allow for evaporation.
The complete Grindal Worms Culture Manual in a PDF file can be downloaded here.