Freshwater rotifers are very easy to raise. The one I have is Philodina but others should take the same care. I also raise Paramecium using this same method. You can use just about any size container for culturing. Just depends on how much you need. I use half gallon glass jars but I have a friend that uses a 20 gallon high aquarium (for some reason this size/shape tank works better than others we've tried).To start - add a starter culture to your jar (or whatever) of tap water. Use tap water or bottled water not aquarium water to prevent contamination. Add a few dry split peas - I use 3 or 4 in the half gallon bottles. Then add a small pinch of dry baby cereal. Continue to add the baby cereal daily unless the culture starts to smell bad. This means you've overfed. Just don't feed for a few days and everything will be fine. Add more peas as the old ones disappear. Within a few days to a week you will see a cloud of rotifers. These can be removed with a turkey baster or small siphon (a piece of airline tubing works well). Since they live in freshwater just put it right into the fry tank. The rotifers live until eaten.
Do not aerate the culture. They will do much better in "stagnant" water. It doesn't matter if your just using a small jar or a large tank. Also - no filtration. You'll just end up filtering the rotifers and their food out of the culture. The baby cereal and split peas that are fed to the culture "decay" and the resulting bacteria etc. are what the rotifers feed on.
Cultures can be ignored and left to go dormant for long periods. When you need them again just add a little fresh water and food and you should have them going again shortly.
I've had mine going from the same starter culture for 20+ years. The person I got them from had them for over 10 years before that. So it is not to hard to keep them going long term. It also costs next to nothing.
Since I've gotten these (and microworms) I use almost no baby brine. I buy eggs in those tiny little vial they sell in most pet stores and they usually go bad long before I use that many.
John Mangan