Worm-Like Creatures in my aquarium

Question
Hey Dillon, hoping you can help out on this here. Last night I fed some freeze dried brine shrimp to my fish. I have 1 Betta,  3 Corydoras, and a Zebra Nerite. They are in a 10 US gallon tank. As I crushed and fed this brine shrimp, within about 30 seconds, I started to notice a few worm-like creatures moving in the water. These worms have a black head and a clear tail with dark rings. They seem to spring, then bunch into a ball, straighten out and spin some more, trying to get to the surface. I managed to capture about 8 with an eye dropper, and place them into a shot glass. Within an hour or so, these worms then turned into little green flies. They never flew off, but sat on the surface of the water.

At a minimum, I do water changes once a week, I currently do 25% every other day trying to get what's left of the Tannins out of the water from the driftwood added over a week ago. I vacuum the gravel with each change. I also use some of that changed water for a small tank that I house a ramshorn snail in. I have never before seen this in either tank.

It was suggested that the Brine Shrimp, being high in nutrients, brought these already existing "nematodes" out of my gravel in search of the smaller pieces. I haven't been able to find any information of nematodes truning into flies yet though.

Any thoughts as to what these are, how they got there, and if they are dangerous to my fish, and snail?

Answer
Well i have never heard of these before, but i would say they are some kind of larvae that got into your tank. I'm sorry i couldn't help you furhter, but they shouldn't hurt your fish so don't worry to much.

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