I was checking out my aquarium today, and decided to scoop out a water sample and take a look at it more closely. What I discovered were numerous, very, very tiny white worms (?) swimming around in the water.
The worms hover around 1 mm or smaller, almost invisible to the naked eye, with some exceptional specimens reaching nearly 2 mm in length. They swim very fluently, not by wiggling or waving their bodies around, but simply, effortlessly gliding through the water.
I checked them out under a microscope, and recorded some videos. I apologize in advance for the lackluster quality, as I'm not working with expensive equipment here. It took me hours to locate the worms under the microscope, made no easier by how surprisingly fast they are.
Here's a picture:
When I first saw this, I wasn't sure I was looking at the right thing. As you can see in this video, it appears to stay rooted at the tail, while wiggling its head (?) around in various directions. Its most notable characteristic is the two ball-like structures on the front of its body. I have a feeling that those structures will be key here.
This next part was very poorly recorded, but boy did it surprise me when I saw it. Eventually, the worm stretched forward, its head seemingly morphing into three parts (video):
Finally, here's one more clip showing off how fast they can be when they want to (I swear it's not even sped up!). I wasn't able to get it back under the microscope at this point.
Does anyone know what these are, or at least what kinds of worms they might be related to (with respect to the ball-like structures on its head)?
For a little extra background, I found these in my native tank sourced with creatures caught in southern Alberta. The tank contains some longnose dace, which have been a source of concern due to heavy flashing (scratching) ever since I caught them. It makes me wonder if these worms are related, such as some kind of parasite. I'm happy to have them if they're some harmless detritus worm-- any members of the cleanup crew are welcome-- but if they're something to be worried about, I'd prefer to know.