Maggots are fun to grow too and easy. Get a small bit of meat or pet food. Put it in one of those plastic containers with a clear lid (like they put salads in from the deli) and sit in the sun. Leave the lid off (this assumes you don't have pets or small kids who will eat it) for 24 hours to give the flies time to find it, then put the lid on, as it can pong a bit after a day or two
The maggots grow quickly and are easy to pick out. Good for fish who are too big to take notice of white worms.