I have used them in the past and still have a couple packed away some where. Typically most UV filters are under sized and people run too high a flows through them. I found I had to run flow rates of a little less than half of what the manafacturers recommended for good parasite comtrol even used in just a quarantine tank. If the glass cover tubes are dirty at all they perform very poorly. I found them just not worththe cleaning an cost of operation, yet alone the cost of purchase. I would reccomend anyone that purchases on use them only with a quarantine tank, and to buy one with UV tube wattage two too three times or more the recommended size for thetank it will beusedon and that they buy only a UV light that has a built in wiper for keeping the glass tube, covering the UV tube, clean.