OK guys. I don't have any involvement with this company, I just tried their product and it rocks! It's called Scumoff. I have a fiberglass pool (almost a year now) and have fought my scumline. This stuff is great! I lowered my water about 2", brushed this stuff on with one of those 1" foam brushes, waited about 5 minutes, took a rough wash rag and wiped it, rinsed it with pool water and scumline totally gone. Dosen't affect the water (at least not within the hour following) and is so easy. I just thought you guys should know. I'll leave a link. It wasn't easy to find locally but I finally did. $14.08 with tax for a quart that should do my small pool about 5 times.