I purchased an X10 prefilter a few months ago http://www.hottubessentials.ca/x10-spa-water-pre-filter.html. I've used it 2x to fill up my hot tub. The water seems no different wether I use the pre filter or not. I have fairly high iron and manganese in my well water. My iron level is 1.0 mg/l and the manganese is .6mg/l. I have a whole home iron filter in the house, but it looks like it's not working anymore. I'm changing the media in it next week. The water is a yellow colour in my tub. When I fill a clear cup with the hot tub water it looks clear... I'm hoping when I get my media changed it will cure my iron/manganese issues, but I thought the prefilter would catch all the iron and manganese. Guess not...