I get brown stains in my fiberglass pool all the time. I can effectively remove them with oxalic acid, but it always turns the water cloudy for about 3 days. Jack's Magic Blue Stuff also works, but it costs me a fortune at over $20 a bottle. I heard somewhere about using ascorbic acid. Where can I get it in bulk? Is it expensive? Will it turn the water cloudy? Will it get the stain out?