Last thing to do is add 1tablespoon of aquarium salt per 5 gallon into the water to assure that these worms die. Last question, were they just on the glass of the tank or on the fish
They are free swimming then sitting on the surface. I did put three creek minnows in could it be something from them? I've changed the substrate about a week or two ago toke all of it out and replaced it.
ya they might me scavengers that may not harm the fish, i suggest leaving them if they aren't doing anything harmful unless you don't want them. If you dont want them, add 1 tablespoon of aquarium salt per 5 gallon or 2 teaspoon per gallon. Hope this helps