Roger, Glassworms are really the larva of a fly called a Midge. They can be found in large densities in some of the northern lakes in the winter, and even through the ice. When the ice comes off of the lakes, you can sometimes take a large aquarium net, and swish it through the surface of the water along a dock, and it will soon fill up with Glassworms (at least where I'm from). Midges are those anoying flies that form a tornado cloud just above your head when you're by a lake in the spring (Lake Ontario), and when there's a hatch, there's MILLIONS if not TRILLIONS of these little critters.
here are a few links with information about Glassworms
http://www.naturegrid.org.uk/pondexp...y/phantom.html
http://www.northstar.k12.ak.us/schoo...lassworms.html
http://www.nativefish.org/Articles/Glassworms.htm
This is a quote taken from the last link,
IMO, Glassworms would be very similar to bloodworms with regards to nutrition. I think you'd be fine feeding them to fish 1.5" and all the way up to adults. If you can collect live ones, I am absolutely sure that your Discus will LOVE them! And any live food will do them good. I'd give the frozen ones a shot, I'll bet they like them too. If you do try it, let us know how it went.I have also been told by the person who now collects glassworms that they offer a nutritional advantage over brine shrimp. He had the dry weights of both analyzed by a lab and glassworms came out on top in protein. I admit this is hardly an unbiased account form someone who is trying to market a product, but I have seen the positive effects on fish when feeding glassworms. One of the most remarkable changes I have witnessed occurred late this summer on some gilt darters Don and I collected a year ago. By summers end, they were a sorry sight having been feed only frozen brine shrimp. Their bellies were flat and all traces of gold had vanished. Within one month of feeding glassworms, they had all filled out and the rich colors had returned.