I bought this because the water here is INCREDIBLY hard and even buying pre-filtered water doesn't do much. So I did a little experiment. I threw 2 tablespoons into a mesh bag and basically let it "cool" like a tea bag in a 5 gallon jug of room temperature water while I was at work checking before and after. According to the API GH/KH test, both GH and KH dropped from 125.3 ppm to 71.6 ppm in about 9 hours. It was still in the water and hadn't met my fish yet (I was concerned it would reduce hardness too quickly and my concerns seemed valid) but it's a definite difference nonetheless! Unfortunately I didn't check the PH beforehand so I can't tell if it has changed or by how much but I'm looking forward to reducing the hardness so we can put our fish in much better water.
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