When I used to breed Angles (before the rot of big nasty fish set in) I used to grow my own cultures once you have some never paid for them again.
Microworms can be cultured in almost any shallow, flat, water tight container. I grew mine on a cereal we get in the UK called Ready Break but you can use almost any cereal grain, yeast, and water keep damp and spray with water at regular intervals. The culture should be kept in a well lighted area at room temperature, 68-85°F. Microworms can withstand temperatures below 32°F but greater daily production can be expected at higher temperatures; however, cultures last longer at lower temperatures. The microworms feed on the yeast and bacteria produced from the oatmeal. After 3 to 7 days, the surface of the media will appear to shimmer with the movement of the microworms, and they will start climbing up the sides of the container.
I used to get a paint brush and wipe it over them then just waggle it in the tank
This recipe for food for them comes off the net
(1) cornmeal, baker's yeast, and water; (2) baby oatmeal cereal, baker's yeast, and water; (3) Instant Ralston cereal, brewers yeast, baker's yeast, and beer; and (4) baker's yeast and water.