Does anyone know what are these ? Are they parasites or signs of polluted environment ?
Are they worm-like or more like cyclopoida?
Do they move in short jerky bursts?
Looks like planaria to me.
Either planaia or detrious worms. Cant really tell. Do they swik around if you knock them off the glass
What ever they are I would get rid of them asap
Another vote for planaria. All you gotta do is more water changes and usually they'll disappear.
I would say planaria. You could be overfeeding the fish.