I do manage to get my pH drop of over 1.0pH in about 30mins - but use duel CO2 injection for the pH drop period. The vid shows I take no prisoners when I inject the CO2

Hi

@Zeus.
OK, in that case, it raises a question or two. A pH drop of over 1.0 means that CO2 concentration is increasing more than tenfold. As you know, the pH scale is logarithmic to base 10. Therefore a 1.0 pH drop is a 10^1 = 10x increase in CO2 concentration (assuming that KH remains constant). So, if the starting CO2 concentration is 3ppm, then the final CO2 concentration will be 30ppm, which would be the recommended maximum for fish. But, if (for example) the starting CO2 concentration is 6ppm, then the final CO2 concentration will be 60ppm, which would normally be considered to be toxic to fish. So, either:

1 Your starting CO2 concentration is less than 3ppm

2 Can fish 'tolerate' CO2 concentrations in excess of 30ppm?

3 Maximum permissible CO2 concentration varies with dissolved oxygen concentration

4 KH is not constant

5 Some other explanation

I would greatly appreciate any comments that you or others may have. Is my reasoning flawed?

JPC