What did I find in my Outside Daphnia culture?

Today I went out do see what daphnia I could get before I empty the pool they are in. When I brought them in I started feeding some to my fish and saw something I hadn't seen before. It looked like a worm with a tail. Before I could get a net to remove it it was eaten. Does anyone know what that might be. I did find a few more in the bucket with the dapnia. They seem to either float on the surface, move along the side of the bucket, or swim with a back and forth motion. If you can identify these are they harmful or beneficial to the fish? If they are beneficial would I want to culture them?

Thanks for any help.

Did they look anything like these?
http://en.wikipedia....t-tailed_maggot
http://www.kensbaita...ges/mousies.jpg

Did they look anything like these?
http://en.wikipedia....t-tailed_maggot
http://www.kensbaita...ges/mousies.jpg

Yep.That's it.I think after reading that first link I will get rid of them.Thanks.

They make good fish food...