Why bother with live food? With all the various kinds of prepared flake fish food available, it would seem your fish could get a balanced diet without resorting to raising worms or flies. The answer is that you can maintain a healthy aquarium on prepared foods, but that varying the fish's diet with live food can enhance color, activity, and breeding success.
For the very newly hatched fish, live food is absolutely necessary. Then, too, if you feed your fish food that will live in the aquarium, the chances of overfeeding become less. And if you're willing to take the time to maintain cultures of living species, it will cost less.
The maintenance, of course, is also one of the downsides - as is the yuck factor in dealing with picking the worms out of rotting culture media, and the chance that some of the creatures you raise might carry a disease or parasite into the tank.
Cheap, Easy and Clean
To feed these to your fish, take a pinch of them and drop them in the tank, or use tweezers to grab them. They will fall in a bundle to the bottom of the tank where you can watch your fish feed on them. Once again, drop in only as much as they will eat within a couple of minutes. Feed this a few times a day.
The culture will last a couple of weeks, after which it will begin to become pretty rancid, so you'll probably want to discard it, keeping a small amount in order to begin another culture.
Clean But Difficult
The life cycle of brine shrimp can depend upon the water quality and conditions in your tank, but when you first start out, you'll usually receive a packet of dehydrated artemia cysts. In the cysts lie dormant embryos that will resume their development once they have been re-hydrated. These can remain viable for many years, providing they are kept dry and unexposed to the air - a container in the refrigerator keeps them well.
What makes these difficult to maintain is that they require a separate aquarium setup which has to be carefully maintained. If you can do it, however, these make a healthy food for both small and large fish.