Use a charcoal filter like Brita to filter out chlorine and other junk. I use this that goes on a garden hose, good for 8000 gallons. I use it for my hot tub but also for my 60 gallon RDWC. should be able to grab one at any tub/spa/sauna or RV dealer/accessories. I do a mix of 70% Tap 30% RO as my ppm out of tap can range between 200-260 (too hard)
you wont be putting much dent in the ppms with charcoal. what you need is a test or report from your water treatment plant which lists the alkalinity/calcium content of your water. This is what keeps your water buffered, PPM reading will give you only an ballpark on buffering capabilities.
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