I've been keeping (culturing? rearing? whatever is proper verb for these worms) for a year or so. Just to see if it can be done.
There are many setups on the Internet. I started from most sophisticated one and finally it get reduced to very simple. The culture is flow-trough system from my FW tank. Very slow drip, which work as food source and water changes.
Main problems is they are slow to propagate. They propagate because I see small worms. I only use very little to feed my fish. If you want to really feed daily, then you need a large setup.
Second problem for me is keeping temperature low, since they're in my garage. I cool them using small computer thermoelectrical cooler.
In short. If you can buy them, then don't mess with culturing.