Grindal Worms, Enchytraeus buchholzi, are annelid worms that are great for feeding fish fry. Grindal worms were first isolated from White Worms by Mrs. Morton Grindal in Solna, Sweden, in the 1950s. This is surprising, considering how different Grindal Worms are compared to White Worms. As you can see from the photo of one of our starter Grindal Worm cultures below, they are much smaller than White Worms.
Grindal Worms have become one of the most popular live fry foods in hobby aquarists and aquaculture. The popularity of Grindal Worms is due to their numerous favorable characteristics as superior live fish food. First of all, Grindal Worms measure approximately half the size of White Worms. This makes them an ideal candidate for feeding fry that has outgrown smaller foods such as Microworms and Vinegar Eels.
Grindal Worms serve as a valuable food source since fry in this stage is still mechanically limited from consuming larger White Worms and other commercial food sources. However, Grindal Worms are not merely a transitional food as they are very nutritious as well. Grindal Worms’ nutritional value is superior to many traditional food sources for the fish fry. In fact, their high protein content has been shown to allow the achievement of peak growth rates for the development of the most robust specimen.
A worm feeder can oftentimes aid in efficient feeding. Another favorable characteristic of Grindal Worms is its prolific nature. Grindal Worm cultures can provide an abundance of food for a fish fry when necessary conditions are satisfied. Every Grindal Worm produces approximately 1000 offspring in its lifetime. Since Grindal Worms are hermaphroditic, containing both male and female reproductive organs, the entire population can produce their individual cocoons full of eggs.
The preference for relatively warmer temperatures also contributes to the prolific nature of Grindal Worms. Grindal Worms prefer temperatures in the range of 20 – 30 °C.
Grindal Worm Size
- Length: 7 mm
- Diameter: 0.5 mm
- Protein: 70%
- Fat: 14.5%
- Minerals: 5.5%
- Carbohydrates: 10%
Grindal Worm Culture
Grindal Worms can be cultured in a variety of containers. The container should allow air exchange but prevent other insects from contaminating the culture. Wooden boxes provide great moisture control and air exchange at the same time. However, plastic containers with ventilation holes can also be used. The opening of ventilation holes should not exceed 2 mm to prevent external contamination. An alternative method is to make a larger opening with a sponge or cloth stuffing.
Grindal Worms are cultured in a mixture of potting soil and peat moss with a 1:1 ratio. Only organic potting soil without chemical fertilizers should be used. The peat moss is used to aid in moisture retention. The pH of the culture media should be maintained at 6.8 – 7.2. If the culture is too acidic, either decrease the peat moss ratio or boil it before adding it to the mixture. The soil must be maintained moist at all times.
If the culture is too dry, Grindal Worms will start burrowing deep into the soil in search of moisture. At this point, the growth and reproduction rate of Grindal Worms will drop significantly. If the culture is too wet, there will be a strong odor due to a lack of oxygen. Wet cultures are highly prone to crashing as well. The optimum soil humidity is 18 – 23%.
Alternative soil-less cultures include coconut fiber cultures and sponge cultures. In soil-less cultures, it is necessary to pay special attention to the moisture level. Grindal Worms should be provided with a constant food source to maintain peak production. However, at the same time, overfeeding must be avoided to maintain a healthy culture. Thus, small frequent feeding is the key. This rule holds true, especially for new cultures.
The following are some of the food that can be fed to Grindal Worms:
- Trout Feed
- Dry Cat Food
- Mashed Potato
- Mashed Carrot
- Mashed Banana
Harvest Grindal Worms
To harvest Grindal Worms, place a glass or mesh sheet on top of the food. This will make it possible to swipe the worms off the sheet as the Grindal Worms climb on it. Mature cultures should be harvested regularly to prevent overcrowding, which can lead to crashing. It is important to monitor and maintain a Grindal Worm culture regularly. The key to a healthy culture is identifying and addressing problems as quickly as possible.
Mites in Grindal Worm Culture
Some of the common issues with Grindal Worm cultures are mites and mold. Grindal Worm mites are very common, especially in cultures with a soil-based medium. While it can be difficult to eliminate mites in a soil-based culture completely, the mites population can be controlled effectively through various methods. While manually removing individual mites can be tedious, clumps of mite populations can be removed while congregating on a food source.
Another method of removing mites in Grindal Worm culture is temporarily flooding the entire culture. Mites can be effectively removed from the culture as they float on the water’s surface. For a culture with excessive mites, re-culturing may be a better option. While removing mites is sometimes necessary, the key is to control the population of mites by moisture control and preventing excessive food left over. To achieve a completely mite-free Grindal Worm culture, a soil-less culture is more realistic.
Another common issue with Grindal Worm culture is mold. Similarly to mites, mold can be controlled by moisture control and preventing excessive food left over.