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 1950’s. This is surprising, considering how different Grindal Worms are in comparison to White Worms. As you can see from the photo of one of our starter Grindal Worm culture above, they are much smaller compared to White Worms.
Today, Grindal Worms have become one of the most popular live fry foods in both hobby aquarists and aquaculture. The popularity of Grindal Worms is due to their numerous favorable characteristics as a 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 have outgrown smaller foods such as Microworms and Vinegar Eels.
Grindal Worms serve as a valuable food source since fry in this stage are 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 source for fish fry. In fact, their high protein content have shown to allow achievement of peak growth rates for the development of the most robust specimen. A worm feeder can often times aid in efficient feeding. Another favorable characteristic of Grindal Worms is its prolific nature. When neccessary conditions are satisfied, Grindal Worm cultures can provide an abundance of food for fish fry. Every Grindal Worm produces approximately 1000 offspring in their lifetime. Since Grindal Worms are hermaphroditic, containing both male and female reproductive organs, the entire population is able to produce their individual cocoons which are full of eggs. The preference of relatively warmer temperatures contributes to the prolific nature of Grindal Worms as well. 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 ratio of peat moss or boil it prior to 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 both the growth rate 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. In order to maintain peak production, Grindal Worms should be provided with a constant food source. However, at the same time overfeeding must be avoided in order to maintain a healthy culture. Thus, small frequent feeding is the key. This rule hold 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 will climb on it. Mature cultures should be harvested regularly to prevent overcrowding, which can lead to crashing. It is important to regularly monitor and maintain a Grindal Worm culture. The key to a healthy culture is to identity and address 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 completely eliminate mites in a soil based culture, mites population can be controlled effectively through a variety of methods. While manually removing individual mites can be a tedious task, clumps of mite populations can be removed while they are congregating on a food source. Another method of removing mites in Grindal Worm culture is to temporarily flood the entire culture. Mites can be effectively removed from the culture as they float on the surface of the water. For a culture with excessive mites, re-culturing may be a better option. While removal of mites are necessary at times, the key is to control the population of mites by moisture control and preventing excessive food left over. In order 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.