no copper no algae but the water is green

[poolish]

hello there.
I've one friend who owns a pool. it is 25,000 gallons, vinyl liner pool . According to her she test her water in a test center and they didnt find out copper (The copper level is 0).In addition, the other levels of chemicals normal. However, she says there is no green algae in her swimming pool but the water is green. and when she uses the stain magnet stuff the water becomes clear in seconds. this is a weird situation. do you think what causes the green color? she has this problem during 2 years.

[Swim Today]

If stain magnet is solving the problem then the discoloration is from a mineral or metal content. Copper is not the only mineral that can be found in water it just is one of the more common ones. There is also iron and magnesium to name a few. Tell her to add a mineral/metal remover to the water. Any pool store should carry one. If not you can find them on my site listed below. The stain remover is more for surfaces then actual water filtration.
Also not to entirely rule out an algae bloom be sure to feel the sides of the pool. If they feel slimy and slippery then it is algae and add a strong algaecide like a mustard algaecide to the water