Put the babies in a small (one gallon jar) and put the jar in the tank with a lid on it. Cut a hole in the lid for an air stone and put some smaller holes in the lid for water transfer (you want the lid of the jar to be an inch under the water level of the tank.
You could also set up a small tank and fill it 95% full of tank water from your angel tank and then the rest of the way with treated or filtered water (to get rid of the chlorine or chloramines). Then when the babies are too big to be eaten you can put them into the main tank or wait until they are a little bigger and sell them to your local fish store.
Doctor Foster's and Smith pet supplies sell an in tank refugium:
you could build your own or use the glass jar idea to make a less expensive one.
The reason for putting the jar in the tank is to keep your tempuratures constant.
Hope this helps,