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19 Oct - CAKC meeting hosted by Cris Diaz, Aberdeen, MD 21001

For Club details contact Cris Diaz - diazcva©aol.com


by Adrian R. Tappin
reprinted with permission
Orinigally published at: http://www.powerup.com.au/~tappin/

Whether you are a general fishkeeper who has had an unintentional spawning of fish in your aquarium or a hobbyist fish breeder with a well-planned breeding program. To raise fry successfully, or even to raise them at all, you must have the right foods available. Having such tiny mouths, the size of the food is crucial to their surviving the most difficult period in their lives. Microworms are just one of the many excellent foods available for feeding fry. They have the added advantages of being easy to culture and will live for six to eight hours in freshwater, by which time they should all have been eaten. Microworms are not suitable as a first food for all fish; some fry are so small that they will require microorganisms. Therefore, some basic research is required before attempting to breed any species of fish. Microworms Panagrellus redivivus (=silusiae) have been cultured since the mid 1930's by aquarists as a live food for a variety of fish species. Their small size and ease of culture has received renewed attention in recent years with rising costs and declining hatch rate of brine shrimp eggs sold in the aquarium hobby

Microworms are a tiny nematode about 0.5 to 2.0 mm in length and 0.05 mm in diameter. When cultured under the right conditions they will multiply in vast numbers. Microworms like it warm and a temperature range of between 25 and 28° Celsius is about right. Although they will tolerate cooler and warmer temperatures, they will not increase in numbers as well. I have been culturing microworms for many years and over this period I have tried several different culture mediums. Bread soaked in beer, yeast blends, and a host of other foods. There are almost as many different culture methods for microworms as there are aquarists, each having their own successful anecdote. I will outline some of the more successful methods I have used. What you have to do is find one that suits your particular needs.

To culture microworms, you will need a small plastic container with a snug fitting lid. Any type will do, from take-away food containers to ice cream containers. I use square four litre plastic ice-cream containers as shown above. It is a good idea to have at least two cultures running at the same time. Start your second culture one or two weeks after the first. You will often find that a culture will sometimes rapidly decline in production of worms. Having a second culture in production will ensure that you have worms available at all times.

Research has shown that the type of culture medium used has a dramatic influence on worm yields. One such trial was conducted using three mediums - wheat flour, oatmeal, and cornmeal. Yield of worms in wheat flour was significantly greater than in oatmeal or cornmeal. Production of worms stopped after day 20 in cornmeal, day 33 in oatmeal, and day 53 in wheat flour. The addition of yeast during initial media preparation was found to have no effect on worm yields. However, the addition of yeast on a weekly basis to the wheat flour medium gave a significant greater yield of worms than did untreated wheat flour. Wheat flour is mixed with water to form a smooth paste and placed in a suitable container. After inoculation with live worms, the addition of 5 ml of a yeast solution, consisting of 7 gm baker's yeast dissolved in 70 ml water; is lightly sprayed over the medium every 7 days. More recent studies on enriched media for microworms has shown encouraging results. Microworm grown on wheat flour plus w-yeast contained a higher percentage of fatty acids.

Another method is to use rolled oats cereal (porridge), normally used as a breakfast food. Cultures are grown on a 1.5 cm thick base spread over the bottom of a plastic container. I use one cup of oats with one cup of water. The mixture is then placed into the plastic culture container and microwaved on high setting for three minutes. The mixture is then allowed to cool to room temperature. After the mixture has cooled, place the starter culture on top of the porridge. Within two days you should see the surface moving. If you use a magnifying glass, you will observe hundreds of tiny worms. You can increase the production of worms by sprinkling dry yeast powder over the surface of the mixture. You do not have to add the yeast until after about two weeks, then once a week should be sufficient. If the culture medium becomes very watery, you can add a slice of bread to the container to soak up the moisture. The addition of bread has a similar effect as does the bakers yeast.

Yet another method and the one which I now currently use requires only a slice of white bread and brewers yeast. This culture method has produced the best results for me. Firstly, cut the crusts off the slice of bread and place it squarely in the bottom of the container. Mix 5 grams of brewers' yeast with 1/4 cup of water and pour the mixture onto the bread, making sure that the bread is completely saturated. It is important that there should be very little excess fluid in the container - about 1 or 2 teaspoons should drain to the side when the container is tilted. Next add the starter-culture of microworm, by spreading it over the surface of the bread. Replace the container lid securely, and place the container in a warm area. Within three to four days, the culture should be thriving with worms migrating up the side of the container. As the bread is consumed another slice can be added to keep the culture active. After the addition of around 2 or 3 slices of bread the culture will need to be replaced. If the culture becomes too wet, more bread should be added to absorb the excess moisture. Remember the wetter the culture, the lower the production of worms.

I have always punched small holes in the plastic lid of my culture containers to allow for air circulation. This has produced a second food for my fishes as during the warmer months of the year I often find other small worms in the culture as well. This is because the odour of the culture will attract the common housefly, which lays its eggs through the small holes of the container lid. The eggs then hatch and the worms develop and grow on the culture medium. This may seem a little unpleasant to some people, but these worms are ideal for larger species of fish, which love them. Their development doesn't appear to have any detrimental effects on microworm production.

Worm harvesting is a very simple procedure. Wait until the worms are climbing the container walls and you will be able to collect them by running your finger around the walls. If you find this method a little unpleasant, then you can use a small stiff brush. The worms can then be fed directly to the fry by swishing your finger or the brush in the aquarium water. Do not dip the brush in the culture medium to collect worms, as any medium rinsed off into the aquarium will only pollute the water. Another method of harvesting is to lay wooden ice-block sticks on the surface of the culture. The worms will crawl onto the sticks and you can then swish the stick in the aquarium water.

Do not forget uneaten worms will die and pollute the aquarium water, particularly in a small aquarium. If left unattended, it can decimate an entire batch of fry in a matter of hours. To prevent this problem, try feeding the fry three or four times per day in small amounts rather than one or two large ones. In all, microworms offer a cheap, simple and nutritious food for feeding a variety of fry. Microworm has as good if not better nutritional profile to that of brine shrimp nauplii; containing 48% protein, 21% lipids, 7% glycogen, 1% organic acids, and 1% nucleic acids. Approximately 70% of the lipids are fatty acids and the remainder is phospholipids.

© Copyright 1996-2000, Adrian R. Tappin - All rights reserved.
Updated December, 2000.