Flukes (Flatworms) Crawling On Tank- Dangerous?

[trianglekitty]

I was just doing a water change and had poured some of the dirty water into a smaller container. I noticed very small white flatworms on the glass- quite a number of them.

I've been losing guppies lately to something that seems like a parasite- they get skinny and have pale feces, then die. Could these flukes be the case? I'm treating with General Cure, so I'm thinking that will get rid of them? Or are these just normal tank inhabitants, and not responsible for my losses?

They don't look quite like the Planaria in the hitchhikers guide...these are pure white instead of gray or transparent.