Daphnia is fairly simple to culture. They may be cultured in anything from 1 gal jars to 55 gal drums. They can tolerate a wide range of temperatures. They can even sit outside or in the garage during winter as long as the water doesn't freeze over. I have them in a 10 gal aquarium sitting outside in the Texas sun so I know that they can take fairly high temps also. For Magna, i find that to reach an acceptable population density to be able to harvest regularly, that they should be cultured in at least a 10 gal aquarium. Pulex and Moina may be cultured easily in 2-1/2 gal aquariums or mason jars. Or if you have some space and you want a really low maintenance culture, just fill an old plastic wading (baby) pool and leave it out where it gets direct sunlight. As soon as the water turns green, seed the culture with daphnia and just leave it alone.
Although it is not absolutely required that you provide agitation to the water, but i find that some agitation helps keep the food in suspension and also helps aerate the water a little bit more. This is usually easily done using a rigid airline tubing and a steady stream of air. The water should not be turbulent such that the poor daphnia are being tumbled too aggressively. Just enough air to move the water around. No filtration is needed.
