I found some very inexpensive fluoride filters at Amazon. The Amazon product page said that they reduced fluoride by more than 85 percent. When I tested them, they didn't reduce fluoride at all. See the video below. 

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• The filters that actually did work are available here at Amazon (ProPur, 9 inch). 

• The tester I used is also available at Amazon here, but you might be able to get it cheaper at Ebay. 

• If you decide to buy the tester, here is a good video that shows how to use it.