The babies are now six weeks old and they're getting hungrier. That is terrific news, as it means they are now ready to be weaned off live brine shrimp and onto fish flakes. They must be able to eat fish flakes exclusively before they can be brought to the pet shop and sold.
The purpose for feeding live shrimp when they are newly hatched is two-fold: the tiny live shrimp are the only things small enough for their mouths when they are first hatched, and instinct tells them to go after the shrimp swimming in the water. Fish flakes and dried brine shrimp, on the other hand, first float on the water before falling.
Soon they will be eating from the surface of the water.