Grow little guys... grow.
Join Date: Mar 2008
Location: Chicago, IL
I have read, in the past, that pH swings caused by changes in carbonate hardness (kH) affect fish more than pH swings caused by the addition/removal of acids. Therefore, adding or removing CO2 (carbonic acid in the tank) is less of an issue than, say, suddenly adding significant amounts of calcium carbonate, or sodium bicarbonate (which affects the kH).
In my personal experience, my fish have endured occasional pH swings between 6.5 and 7.5 with no harm. The swing is due to CO2 de-gassing when doing maintenance. On a daily basis, however, the swing is always between 6.4-6.5 using a pH controller. All my fish (zebra danios and tiger barbs) are more than six years old with no diseases, they have great colors, and general vibrancy. But since I always prepare my own aquarium water using RO water as the foundation, I design the kH to always be around 7 degrees (125ppm as CaCO3).
So, in my case, the kH has been fairly constant for years, while the pH due to CO2 content has been all over the place (pH 6.0-8.0).
Jeremy Squires, Toronto, ON
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