I recently moved & reset up a 30 gal. tank. Over the past 2 months, the PH in the tank has drifted upward as has the hardness. I live in NYC where the tap water is neutral and fairly soft.
Before the move, the hardness was routinely 70 to 70 ppm. Now it is more like 110ppm. The PH is about 7.2-7.4 although it is hard to tell with my cheap test kit — the solution just looks blue instead of green or yellow). The only change I can think of is that I added some laterite to the gravel when I reestablished the tank. As I understand it, laterite has lots of iron, but it should not be soluable & should not affect the PH.
Any thoughts? (strictly speaking I guess this in not an apisto question, except that I do keep dwarf chiclids in the tank).