little spiralling worms
This could describe any number of worms. It's kind of like saying you found a little shrimp or a little fish. If you can't take a picture of them, then it would be helpful if you could give a detailed
description of them. What color are they? How big are they? Where are they in the tank? How do they appear to move? Do they "inch" around like an inchworm or wiggle or what? Get a magnifying glass to look at them up close to get a better view of their body shape. Are they flat or round? What's their tail look like? Their head?
The better you can describe them, the better chance you have of getting help. Otherwise, the best anyone can do is throw out the names of a bunch of different worms, and you'll have to look them all up to figure out if any might match what you have if you.