This is a feeding of live artemia given to angelfish fry that are a few weeks old. The lighter colored fish are the koi from a Koi/Wildcross mating.
Our procedure for feeding artemia is to feed once, maybe twice per day for the first week after free-swimming. Then, twice per day for the next few weeks, when we then transition them to dry foods. To transition, we feed artemia in the morning, and then no artemia in the evening. Instead, we put in a very small amount of fry-sized dry food - but not nearly enough to feed them all even a little bit. After 2-3 days of this, they are vigorously seeking the dry food and we then start adding a bit more each time. Within a week, we can completely remove them from live feedings of brine shrimp if we choose to.
As always, comments are encouraged.