Looking at my goldie tank today I saw some small worms/larvae in there. One type was about 4mm, white, and floating at the top; probably midge larvae. The other was the same size, bright red, two-thirds of the way down the tank and swam in a looping manner. I did some research that made me think it might be a bloodworm, but they're listed as being 15mm long. Is it likely that it's a small one? I don't feed any live foods.