They can easily live in your tank for long periods if uneaten. A starter culture is need to start a colony. Daphnia can be cultured in any size container. We use 10 gallon tanks and one gallon jars to raise our daphnia. The easiest way to jeep a daphnia culture going is to use aged green water or heavily aglaed water.
Daphnia eat the infusoria and other microorganisms which grow in such water.
You can also feed your mother daphnia cultures dried brewer s yeast, powdered milk, pumpkin pulp, or squash pulp. Avoid vigorous aeration of the culture. Daphnia generally purify water and the fry will eat them as they grow to sufficient size. A shrimp net or a fine fish net can be used to catch Daphnia. Invert the net to feed.