My 20 long has a Ph that runs between 6 and 6.4, and for the fish I have, that is fine, but I would like to know what could be making it so low. The tank is cycled. No ammonia, no nitrites, between 10 and 20ppm nitrates every time I test. My decorations are slate rock that has been thoroughly cleaned, a fake driftwood decoration, and my substrate is sand. I know that the ph is not coming from the tap water, because not only have I tested it, but I also maintain my 10g with the same water, and its ph is 7.2. My filter is a Marineland Penguin 200b, and my stock is 3 Julii Corys, 7 Harlequin Rasboras, and 1 Threadfin Rainbow (and yes, I am getting him friends, but the LFS
only had one in stock!). I can't figure out anything that would make my Ph go as low as it is!