Small white worms in my aquarium!!!!

[Dorey]

What are they Tiny little wiggly worms. Are they parasitic? My tank has been set up and cycled for three months. I have five large fancy tailed goldfish one of which has a alinear growth/swelling running from dorsal fin to halfway down the side of her belly. She has been like that since i inherited her in march of this year, the eye on the same side is all black and slightly bulging. All this time she has been , as i see it, fine. eating well, grazing, socializing, relaxed into the community. Two days ago there seemed to be an opening in the top half of the growth so i added WATERLIFE PROTOZIN to combat fungus then, last night, three stringy bits were hanging out of the bottom of the growth. This morning they were gone, but, I saw lots of little tiny white worms in the tank. i went to my local fish shop and they suggested is try JBL ARGUDOL as a one off dose. What do the knowledgeable ones think

[chefkeith]

Planaria, tiny non-parasitic worms, live in the substrate in most well established tanks. Sometimes they can be seen crawling on the glass too.
IMO, they are an essential part of the food web and biological diversity in an ecosystem or an established aquarium.

[Dorey]

Thank you very much, so the Argudol I bought is not needed.