Please retest GH and KH so we can see which of your other tests they are closer to. Also please test your cold tap water for GH and KH, and pH while you're at it to see if there's a difference. A lower GH in the tap water would indicate something being added to the water in the tank, like from a rock or the substrate. What is the substrate, btw?
Oh, I don't know if sandstone is particularly basic. A rock containing Calcium would be more likely to contribute to the GH. To be sure, and if someone knows about sandstone please chime in, take out the sandstone rock, dry it off, and pour a few drops of vinegar (acetic acid) on it - if it fizzes, it's no good.
I don't think the fluctuations have anything to do with the cycle. A GH of 14 is pretty hard water - 7 is much better. KH of 3 is as low as you can go without risking pH swings. My KH is about 3.
GH and KH tests can be hard to measure. Use good light and a piece of white paper to do the tests and see the colors. Let's see how new tests come out.
Steven
Oh, I don't know if sandstone is particularly basic. A rock containing Calcium would be more likely to contribute to the GH. To be sure, and if someone knows about sandstone please chime in, take out the sandstone rock, dry it off, and pour a few drops of vinegar (acetic acid) on it - if it fizzes, it's no good.
I don't think the fluctuations have anything to do with the cycle. A GH of 14 is pretty hard water - 7 is much better. KH of 3 is as low as you can go without risking pH swings. My KH is about 3.
GH and KH tests can be hard to measure. Use good light and a piece of white paper to do the tests and see the colors. Let's see how new tests come out.
Steven
