Many vendors sell pre-made fruit fly media (food) and complete culturing kits. But, you can mix up your own media from ingredients found at your local grocer. More on that later.
Here's the basic steps to start a new culture from an existing starter culture.
Mix the 1/3 cup dry media with 2/3 cup of hot water. The consistency should be like stiff oatmeal, you should be able to turn the container upside down without the media falling out or running down the sides.
Then add a baseball size ball of excelsior or a few folded coffee filters into the media. This serves as a substrate for the maggots to climb out of the media and pupate on.
Allow the culture to reach room temperature, before adding flies. You should add approximately 50 flies for each culture. Male Hydei need at least 9 days to reach sexual maturity. For Hydei it is best to use a mix of old and new cultures.
Cultures should be maintained between 70 and 80 degrees for best production.
The cultures should be placed on mite paper and in an area where they will not dry out. Mite paper can be made by spraying paper towels with mite spray and allowing it to dry thoroughly, or you can purchase shelf liner paper that is already impregnated with insecticide. Dusting your flies before adding them to a new culture will help to eliminate any mites from your older cultures.
In a week or so, the maggots will be ready to begin to transform into flies. These cultures are 8 days old, as you can see there are plenty of pupae; which will hatch out in another few days. Melanogaster produce in approximately 10 days, Hydei at least 14 days. It is best to dispose of all cultures when they reach 30 days old to prevent mite infestations. The containers and lids can be bleached and rinsed for reuse many times.
6 Parts Instant Potato Flakes
1 Part Brewers Yeast
1 Part Powdered Sugar
Some people add some cinnamon to their cultures to make them smell a little better.
Commercial Fly Food usually contains a mold inhibitor, methylparaben. You can add about a tablespoon of vinegar per culture to keep them from molding.
If you have difficulty finding any of these ingredients, let me know and I can help you out.