After a few days the microworms will break down the food ball and it will spread out to cover the dish. In another couple of days the worms will start crawling up the sides of the dish where they can be harvested. Just use a tooth pick to scrap off the microworms and swish it in the aquarium with the baby fish. The microworms will slowly sink to the bottom of the tank.
Over time, the microworms will continue to break down the food and it will become a thinner liquid. Add a little more dry cereal when it gets runny. This will boost worm production and extend the life of the culture.
After about 4-6 weeks the culture will start to turn brown and production will decrease. That is the time to start a new culture. Once the new culture is producing, you can throw the old one out.
There are a couple of other worms types similar to micro worms including Walter worms and banana worms. They are different species. There have been over 28,000 species of nematodes described, There is a bit of difference in the size but it is probably not critical in most cases. I have found that the banana worms are more productive but the cultures go bad faster. You might have different results. Try all three to see which work best for you. It may not make sense to keep cultures of all three.
Microworms make a great compliment to baby brine shrimp for feeding newly hatched tropical fish. The effort to culture them is definitely worth the effort.