Loaches Online Forum

Some filters exchange minerals in the water for minerals held on the filter media. The swap is 2:1, so the TDS of the filtered water can indeed be higher than the filtered water. This is common in a sodium exchange water softener. It removes calcium and magnesium and adds sodium.

Wow, I had no idea! Thanks for the explanation - guess I won't get rid of the filter then

Just do a little research to see if this produces water that is really better for your fish.
Look up the brand and model of filter you have, and read about how it works.
Test the unfiltered tap water and see if it really needs any treatment at all before using it for an aquarium.
Post all the test results here, and lets see what you have.
GH, KH, pH, TDS. Include the units in all the measurements.
1) Tap water that is not filtered.
2) Filtered tap water
3) List the fish you want to keep and if it is your goal to breed them.

Diana wrote:Just do a little research to see....

Thanks for your perspective and help, but all I have currently is capability to measure TDS and pH. I'm curious about the GH and KH, but haven't taken the time or money to find a kit yet. I will be sure to keep this in mind, though, and when I finally do pick up a kit I'll be sure to post all the stats/info and ask!