MicroWorms 
By Bettas 'R Us

As soon as you receive your starter culture, set up a larger culture without delay. The temperature should be from 65°F to 90°F. The ideal temperature is 75°F. Any plastic container can be used to culture MicroWorms, but a clear one is best. The container should covered to to keep moisture in but small pinholes should be punched in the cover for air exchange. Also, the cover will help protect the culture from fruit flies that may try to invade. I have found that most holes you can punch, besides small pinholes of a safety pin, are still large enough for fruit flies to invade your culture. To prevent this, you can take a paper towel and place on top of you open container prior to placing the lid on. This will allow for air exchange through the holes, but fruit flies will not be able to get past the paper towel. 

You can use many different cereal-based media for MicroWorms culture, including cooked breakfast cereals, oatmeal (what I use), moistened plain (not self-rising) yellow cornmeal, wheat germ and instant cereal products (i.e. Gerber Baby Oatmeal Cereal - any flavor). To prepare a high yield formula, place dry Quick Oatmeal or baby cereal in a container to a depth of about a half inch. Mix active dry yeast ( 1 - 2 teaspoons) in slightly warm water until the solution is quite milky. This warm-yeast solution should then be added to the cereal and mixed to a thick paste. Active yeast is very important in order to maintain a high yield of of worms. 

Add the starter culture on top of the new culture. Stir the culture every 2-3 days to keep the culture from getting watery. Add a small amount of water to the culture if the surface of the medium is drying out. In four to seven days the worms will have covered the surface of the medium and will start climbing up the sides of the container. At this stage they are easily collected with a razor blade, a brush, a cotton swab,  metal spoon or rubber spatula  (what I  use). They can then be placed in a tank with your young fish. I have found my adult fish (guppies and other livebearers, not my adult bettas) enjoy them too if I have extras. I have also found that by placing the microworms in a brine shrimp net and rinsing them prior to feeding will decrease the addition of culture to the tank.

You have to sub-culture every 2-3 weeks. If you fail to do so, you will end up with a foul smelling mess and a dead culture. To subculture, start a new culture as though you have received a starter culture. Once it is setup, take part of your established culture and add it as though it were your starter culture. The rest can be discarded when it stops producing worms.