How do I remove stains from the bottom of a vinyl liner. This pool has been negleted for 3 years. You could not see the bottom until this yr, they asked me to help get it clean. And they were swimming in it in the past years in cloudy water. They said they have never been able to see the bottom until I showed them BBB method. I am assuming the stains are from algae that sat there for a long time and they have alot of trees.