How can you remove fingernail stains?
One way to remove fingernail stains is to bury your finger nails into half of a lemon for a few minutes. This will sting badly if you have any open cuts on your fingers. One way to prevent these stains in the future is to use a clear base coat underneath colorful nail polish.
I have a fiberglass pool and I am constantly battling with iron stains. It is not impossible to remove the stains. I get brown stains in my pool and I treat them with jacks magic stain solution #1. Check out their website. They show different pictures of different types of stains. The stuff does remove the stains quickly, but it is expensive. Hope this helps.