Culturing Grindal Worms
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Grindal worms are very easy to keep and breed, and make an excellent food for small to medium fish. A typical harvest will contain larger and smaller worms suitable for even tiny fry, and whats more these worms will live happily underwater without dieing and causing pollution.
The worms and media are kept in plastic food storage boxes, loosely lidded. Each culture is fed and harvested at the same time approximately every 24 hours. Cultures live indoors on the top (warmest) shelf of the fish room all year round. It is important to allow the worms ample ventilation; cultures with no air can crash very quickly.
Culture media does not seem to be critical, a blend of coir (45%), peat/compost (45%), a small amount of sand (10%), maybe a handful of lime if you've got it. Cultures will turn acidic eventually and should either be replaced with new cultures if production drops, or partially replaced continuously (I take a few handfuls of media to a fish auction every now and again, and then top up the old culture). If you do not want to subculture too often, activated carbon can be added to the media. The media should always be damp, yet never waterlogged or sodden.
The worms are fed on (under) glass plates. I sprinkle a light layer of instant oat cereal on the glass, and place face down on the culture.
The worms are harvested 24 hours later, simply by running clean water over the glass. The glass can then again be reloaded with food.
Provided cultures are kept warm and well fed they can provide daily worms for months with no real problems. Cultures should be restarted when production drops off. Many people complain about mites within their cultures, and moth balls can be used, however if the food is under a large enough piece of glass this is rarely a problem.
Feeding grindal worms to killifish
Grindal worms make a superb food for most you and medium sized killifish. Quicker growing annual fish such as Nothobranchius will take grindal worms fairly quickly after artemia, often within their first week. Make sure you feed very small numbers if you have a substrate in your tank, as worms will bury themselves, eventually dieing under the gravel.
10 day old Nothobranchius furzeri eating grindal worms This is a still from a short video clip. Click the the image to go to youtube and play the clip. Note there is a high resolution version (just below the image on youtube, look for the 'watch in high quality' link)