I did a 40% water change yesterday. My tank is new but I let it cycle for 7-8 weeks, tested the water chem until it was 6.6 pH, 0 ammonia, 0 nitrite and below 15 ppm nitrate. I’ve had fish in it for about 6 days. The rummies and cardinals were added most recent (this is 3rd day). It’s a planted...