The best/easiest one so far copied direct from source:
Microworms are an excellent food for small fry, and are one of the easiest live foods to culture.
Thanks to Tahia Reynaga for suppying the following detailed method.
live starter culture
one transparent or semi-transparent container with a tight-fitting lid
nail or similar, to make holes in the lid
100% pure oats
pure tap water
active dry yeast
paper towel large enough to fully cover the container with surplus at the edges
I prefer to use a container that is approximately 7x7 inches. Deli counters or salad bars often have good containers that are used for take-away meals. Chinese food delivery meals often come in similar plastic containers. Make sure you find one with a tight-fitting lid and transparent or semi-transparent sides.
Begin by poking some holes in the lid with a nail. The holes should be as wide as the nail. Make about nine holes for a 7x7 container. These holes will allow air to reach the culture. Rinse the lid and container in hot water several times to make sure it is as clean and sterile as possible.
Cook the oats for approximately five minutes, stirring the mixture the whole time. You will want the mixture to be thick but not dry. You should be able to pour it.
When the oatmeal has cooled enough to touch, pour it into the container. Remember that as it cools it will congeal, so you may need to stir in a bit more water to be able to pour it. In order to prevent any flies from entering the mixture, place the oatmeal in the refrigerator while it cools.
With your plastic spoon, take about three teaspoons or so of the culture and spread it onto the oatmeal, which should be cool to the touch, or at least room temperature. Make sure it is cool enough so that it will not kill the microworms. Spread the starter culture around on top of the oatmeal.
Dissolve a very small amount of yeast (just a few grains per culture) in a small amount of warm water. Pour this over the oatmeal. Place your paper towel on top of the container, and then secure the lid onto the container. The paper towel serves to keep out any fruit flies, which would otherwise lay lots of eggs in the culture/oatmeal mix.
Set the culture someplace warm, like on the hood of a fish tank, where the heat generated by the fluorescent lights will stimulate the microworms to breed. In a few hours, check to see if you can see any worms wriggling on the side of the container. Once the culture really takes off, you should set it somewhere cool in order to minimise the smell. When the culture starts to smell a lot, subculture it by taking a small portion and spreading it on freshly prepared oatmeal, as indicated in the above steps.
You can harvest your culture by using your finger, Q-tips, or any small tool that can scoop up the worms. If you take the worms from the sides of the container, you should be able to avoid any oatmeal. I like to rinse my worms by putting them into a small amount of water (tank water is fine). You can then use an eyedropper to feed them to your fry.