Enchytraeus buchholzi

Enchytraeus buchholzi (also known as Whiteworms or Grindal worm) are cultured by aquarists as a fish food. Whiteworms are a popular forms of live food cultured by aquarists. They are used for conditioning tropical fish before spawning, or for young fast growing fish. Some aquarists feel that fish fed exclusively on Whiteworms become obese due to the fat content of the worms.^{[citation needed]} However, the problem may lie more with overfeeding with the worms, rather that the fat content of the worms.^{[citation needed]}

Reproduction

Whiteworms are one of the largest species of the genus Enchytraeus (adults range from 15mm to 40mm (1/2 to 1 1/2 inches) in length and from 0.5mm to 1mm in diameter). They are hermaphroditic, with each individual having both male and female reproductive organs. One worm mates with another individual and each fertilize the other. The worms exchange sperm cells during copulation and eggs are laid in transparent cocoons. Each cocoon produced by young adults contains 9~10 eggs; cocoons from mature adults produce 20~25 eggs. As the culture density increases, the reproductive rate levels off and old worms will only produce around 2~3 eggs per cocoon. The highest egg production reported was in the vicinity of 35 eggs per cocoon. Average per total population in culture is 10 eggs per cocoon. The eggs hatch in 12 days, and worms begin reproducing in 20~28 days depending on temperature. Each individual can produce as many as 1000 eggs over its life span.

Culture

Whiteworms required 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.

Appropriate containers

Whiteworms will usually not survive in acid soils (i.e. < pH 5). 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. Simple boxes made of pine or plywood are generally preferable to plastic, Styrofoam, or other man made materials because the joints allow better drainage and aeration of the soil. However, the current trend for culturing white worms is to use small individual flat plastic food containers stored in an electronic wine cooler, which can be maintained at the desired temperature. This not only provides the ideal temperature, but it also keeps unwanted pests out of the culture.

Temperature

Whiteworms 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. Growth has been reported to occur more rapidly at the higher end of the range with maturity in 28 days at 68°F, the clitellum (The clitellum is responsible for producing the cocoon in which the eggs are deposited) forming when the worms were about 13~14 mm. The maturation period at 46°F was at least twice that at 68°F. Experience has shown that at temperatures above 86°F or below 32°F, Whiteworms will die.

Light and predators

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. Any flat material that can be pressed lightly onto the surface of the soil will serve as a cover such as a thin piece of scrap glass cut smaller than the surface area of the soil. Leave a border of about 1/2 inch of soil exposed to the air. The collection of moisture at the cover attracts the worms, making it an ideal place to feed them. By attracting the worms to the surface for feeding, it will be easier to collect them to feed to your fishes.

Soil characteristics

Whiteworms will grow in any kind of light loam soil of such a character that it does not easily harden when dry, while on the other hand it should not be sandy. Potting mix obtainable from most garden supply stores should be adequate. Choose a good quality mix as some potting soils contain a lot of coarse material in them. Leaf mold and humus are excellent additives that will improve the soil significantly. Some of the best mixes are those that have been designed for growing seedlings. These are generally very fine and hold moisture well, but remain loose. Whichever soil you choose, ensure that it doesn’t contain any chemical fertilizers, sterilizers, fungicides, pesticides and other man made chemicals or contaminants, as these additives will kill the worms.

Container preparation

Fill the box about two-third full with your chosen soil mix. The surface of the soil should be level and pressed down, not too firmly, to leave no lumps above to dry or mold. Afterwards, the soil must be moisturized until it’s reasonably damp, allowing any excess water to drain. There should be sufficient moisture to allow free movement of the worms but not enough to bring them to the surface except as they may congregate on the under side of the piece of glass resting on the surface of the soil.

Getting the culture started

The next step is to get your starter culture. These are often available from aquarium stores, live foods suppliers or from a fellow hobbyist. Once you have your starter culture, empty the contents on top of the media. Sprinkle a small amount of food over the surface of the soil and spray with water. Place the soil cover on the surface, put the lid on and move the box to an area that will stay between 15-21°C. For best results, keep the culture in a cool dark area. If necessary, a refrigerator with its thermostat turned up can be used. Allow the culture to stand undisturbed for several days to allow your Whiteworms to propagate.

Food sources

Whiteworms 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. There are many opinions as to what is the best feed, i.e.:

• Breadcrumbs
• Carbohydrates
• Vegetables
• Fruits
• Commercial trout feed pellets
• A combination of all four of those above
• Out or all the above the greatest numerical increase and best reproduction was found to have occurred with the commercial trout feed pellets, which contained 45-47% protein and 12% fat.
• The least increase in number of individuals was observed in the vegetable-based group.
• Heinz® high protein baby cereal (blended with water) contains higher protein levels than many of the other foods. The cereal also provides higher protein levels than many of the other foods. This higher protein increases the nutritional value of the Whiteworms, which is then passed on to your fish.

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.

Feeding frequency

Whiteworms should not be fed too heavily at first because surplus food tends to attract mites, fungal growth, and bacterial contamination. You will have to regulate the amount of food offered during the first month until the culture stabilizes. Replenish the food supply, as needed (ideally every three to four days). If the food supply is not entirely consumed between feedings, you are adding too much food for the worm population.

Humidity

Upon your regular inspection, you may find that the moisture level of the culture has dropped and that the surface of the soil has begun to dry out. If this condition is allowed to continue the worms will start to go deeper in the soil seeking moisture. When they do this, they are also moving away from the food you place on the surface of the soil.

To counteract this problem, 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.

Other Maladies

• Mold may often be present but does not seem to interfere with worm production if the food masses are not large. Removal of surface growth and taking the cover off to allow short drying periods will help keep it in check. However a souring culture is to be strictly avoided.
• Whiteworm cultures are often infested with mites. These small, spider-like creatures are harmless and will not do any damage other than eating the Whiteworms’ food. If you keep your culture in a refrigerator, then mites will not be a problem.
• After a period of six to nine months, the soil texture will begin to break down due to the activity of the worms, and the soil will become very acidic. This inhibits the production of worms, leaving you with only adult worms. To maintain your culture, the old soil should be removed and fresh soil placed in the box. The culture can be divided into several boxes at this time, as it is a good idea to have more than one culture in operation. You can transfer most of the worms by collecting from the old box and placing them in the new box. Another simple method to replace an old culture is to scoop away the top 2~3 cm of soil with most of the worms and gently mix it into fresh, moist soil in a new box.

Grindal Worms

Grindal worms, Enchytraeus buchholzi (Vejdovsky, 1879) are a smaller relative of the whiteworm, but usually only grow to about 10 mm and thus are an ideal size for most rainbowfishes including both adults and larger fry. Mrs. Morten Grindal, of Sweden, who was prominent in the development of culturing techniques for whiteworms, was apparently the first person to isolate this smaller species. Grindal worms can be cultured exactly as whiteworms 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 (see above) forming when the worms are about 3~4 mm. The generation period (cocoon to cocoon) is about a month at 20°C.

In laboratory testing, Enchytraeus buchholzi were kept in an incubator at 15 ± 2°C. Water loss and food were replenished if necessary during the test period. After 21 days the offspring and the surviving adults were counted. For two moisture levels (5% and 20% water content) the segment number of the surviving adults was counted. From 20% up to 40% water content Enchytraeus buchholzi showed no significant difference in reproduction. Below 20% and above 40%, the number of offspring was reduced. No juveniles were found at 5% water content, although adult survival was equal to higher moisture levels. Reproduction was decreased at 30% water content compared to 25% and 35% water content. Low soil moisture inhibited not only reproduction, but had also a negative effect on the growth of the parent generation.

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