UPDATE: I added the faulty filter's name (AquaCera) to the title of this video on 12.16.17, approximately 1 year after I contacted the company about this follow-up test. I never heard back.
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. I wrote the company and they sent replacement filters...same problem. I then tested a different brand (ProPur), and they DID work. The brand I had trouble with was AquaCera.
The exact / properly working ProPur filters I used are available here: http://amzn.to/2fUwisc
The tester I used is also available at Amazon (here: http://amzn.to/2gWe1M4) but you can probably find it cheaper on Ebay.
If you decide to purchase the tester, I recommend watching this video that shows how to use it: https://youtu.be/qFaX-MDJf_w
