Microworms are extremely prolific and easy to grow at home. Since they are smaller than newly hatched brine shrimp, they are ideal for small fry. Small fry can be given microworms as their first food, while extremely small fry need to feed on infusoria or similar for a while before they can switch to microworms. Many small fish species, such as tetras, will actually appreciate microworms throughout their entire life.

Despite their common name, microworms are not really worms – they are nematodes. Some nematodes make great fish food while other nematodes are parasitic and will cause bad health in fish. The nematodes grown by aquarist to serve as fish food are normally a type of nematodes that feeds on starchy food, such as oatmeal, flour and similar. They are therefore completely harmless for your fish and you can add live microworms to the aquarium without risking the health of your pets.

Culturing microworms
If you want to grow your own microworms, you need a starter culture, some unsalted oatmeal and a suitable box.

  1. Purchase a starter culture from a pet store or contact you local fish club and ask if anyone is willing to give or sell you some microworms.
  2. Make a small batch of oatmeal according to the directions from the manufacturer, but add somewhat less water and cook it a bit longer than normally. You want the oatmeal to be like really thick porridge.
  3. Cover the bottom of your box with ½ inch of the oatmeal. You can for instance use an empty margarine box.
  4. Leave the oatmeal to cool in room temperature.
  5. Pour a pinch of active yeast over the oatmeal.
  6. Add your starter culture to the box. One spoonful of worms is enough to kick-start the cultivation.
  7. Put a lid on the box to prevent insects from entering.
  8. Push a few small holes in the lid to allow moist to escape.
  9. Place the box at room temperature and wait. Within a couple of days, the oatmeal should start to look a bit soupy and smell yeasty.
  10. If everything goes according to plan, you can start harvesting microworms after one week.
  11. Microworms can be kept running for several weeks, but sooner or later the content of the box will develop a deep, dark brown color. This means that your microworms have devoured most of the oatmeal and the box is now filled with excrement and discarded debris. Make a new batch of oatmeal in another box, sprinkle yeast on top and add a spoonful of microworms from the old box.

Harvesting microworms

  • Place the box in a warm place, e.g. on top of your aquarium lights. The microworms will crawl to the top to escape from the heat.
  • Wait 10-20 minutes before using a dull plastic knife or similar to scrape the sides of the box.
  • Place the plastic knife in a water filled jar to rinse off the worms.
  • Use an eye dropper to suck up the microworms and feed them to your fry.