Just don't worry about them... consider them part of the natural look you're going for... and tell your friends that, too. They'll think you're super-cool. I had planaria (they are a nematode) in my 125, and all I had in it was my RTC, at the time. He ate every piece of fish and every pellet that went into that tank. I have heard they come from overfeeding, too, but I can't believe it, now that I've had that happen. There's no way there's leftover food with a red-tail!