What color is it? It could be a planarian if it has a triangle head. They can be incredibly dangerous to shrimp. If it's not a flatworm, it's definitely some kind of worm. If you see it again post a picture and I would take it out.
It was reddish brown and I will take a picture if I see it again. I don’t think it was a plnaria as it was defiantly round and had a head like a earth worm.
It's probably a roundworm. They can be introduced on plants or fish. I'm not share what kind it is but if you see it again, you probably should remove it.
Well, if you see it again, take it out. Definitely don't tear apart you tank! Just keep an eye on your fish to make sure they don't start acting differently.
I would hope its not Camallanus Worms which is a parasitic roundworm.They are very resistance to medications but also very popular in the freshwater aquariums they are also red .The best treatment if it is camallanus would be Levisome .