My filtered tap water has a pH of 7.6. & GH of 150ppm. When put in my tank
with Eco-complete, Silica sand, drift wood, 1 large black rock and a few dozen black river rocks
the pH went up to 8.4 and the GH is at 300ppm (using strips for GH, 300 is the highest they test to). I decided to test the large rock, river rocks, and sand separately. I let them sit in new water over night and tested them in the morning. Large rock: pH 8.2, GH 150ppm; River rock: pH 8.4, Gh 300ppm; Sand pH 8.2, GH slightly lower than 300ppm.
I am very confused. I thought that silica sand is supposed to be inert. I asked my father in law (who is a retired chemist, but knows nothing of fish keeping) and he said there must be something, possibly calcium, in the sand. Does this sound right to anyone else? Has anyone else experienced silica sand raising their pH?
In this tank I'm hoping to keep kuhli loaches and a pea puffer. "Seriously Fish" says the pH for kuhli loaches should be 3.5 – 7.0 and 6.8 – 8.0. for the pea puffer. I'm actually more concerned about the pea puffer, since I've never kept them before and they seem to be more sensitive. Do you think the fish will be okay in the higher pH? I don't want to do anything, beyond the initial setup, to continuously alter the ph (like adding peat, or chemical pH down).