you can call me crazy but i bought the hagen co2 kit and my ph actual rose by from around 7.2 to 7.8 with the co2.
i think it's cause they put baking soda as a buffer, which raises pH.
anyway, all my fish adapted fine since the co2 takes about 2-3 days to really start coming out. they were all fine when the yeast died off and stopped producing co2 too