Do freshwater aquarium sump filters work properly?

Yes, I have a freshwater aquarium, and I installed a sump filter for it a few months ago because the filter that comes with it broke. I was a little worried about using a sump, because even though it is freshwater, the water is running through saltwater sand and gravel. Fortunately, I have not seen any negative effects, and the water quality has been great since the sump was installed. I'm sure you'll be happy with the results.