This is a picture of some kind of worm that appeared in the corner overflow of my 220 gallon tank about two weeks ago. There are now lots of them (you can see a second one in the background) and they are about 1/2-3/4 inches long. The tank has been in operation for at least 10 years, and there have been no new additions for at least a year and a half, yet here is a new organism that must have been biding its time before making an appearance. There are none at all in the display area, only in the overflow. Just curious, does anyone know what these are?