So I have seen a lot of critters in my day but this is a new one.. I have a couple of these small spaghetti size worms about a half inch long swimming wildly in a corkscrew like manner through the tank, they seem to be tough little critters as I watched one get sucked into my circulation pump and after being spit out the nozzle it floated limp through the water for a while before springing back into its spiral swimming pattern only to be grabbed by a fish which chewed on it for a bit then spit it out, again after floating limp through the water it revived and swam into a hole in a rock.. I’m seeing them first thing in the mornings and because of lighting and the speed at which they move it’s hard to get a good picture of them