I can imagine one of the challenge as how to prevent midges escape when nesting the bloodworms out.
Is live bloodworm really irreplaceable? It seems like culturing black worms seems to be easier.
My friend in Hong Kong was always able to put a bowl of water outdoor and eventually find bloodworms naturally in the water. Dont know if this is possible in else where of the world.
Although I have not researched enough, some naturalist in Ontario Canada told me that there are bloodworm in Canada as well. I was surprised at first, cause I never seem live bloodworm for sale in Canadian aquarium.