how much co2 swing is too much?
I have setup a 130 gallon for a week now. The Ph has been 6.5 in the morning and 7.0 at night(before I turn off the lights). Is this too much Ph swing for the fish? (I guess that depends on the fish as well but in general is it too much?)
Also, I have very hard water; 10Kh. At 6.5Ph, it looks like there is 100ppm Co2. Is this bad for the fish?