I belong to the 50% weekly water changing club. I drop my pH a full point in my
CO2 injected tanks, from 7.8 to 6.8. I have pH monitors on my
CO2 injected tanks and my pH usually rises about 0.4 when doing my water changes, it then slowly moves back to 6.8 over a couple of hours after the water change, but the rise happens very quickly. I keep many "considered" sensitive fish such as Apisto's and Chocolate Gourami's. I've never experienced any sign of stress related to sudden and dramatic changes in pH in fish tanks. I routinely move fish from
CO2 injected tanks to non-injected tanks...again no problems in either direction.
I've never seen any problems nor do a subscribe to the belief that there is such a thing as "pH shock". Wright Huntley has some interesting posts on the APD if you search the archives for "pH shock". Here's my take on the issue of pH shock. In and of itself pH swings cause no harm, but the impact of a movement in pH may have synergistic effects. Meaning that it's a combination of two or more substances which produce effects greater than their sum. For example, the pH of the water will determine the toxic effects, if any, of many substances. Ammonia, Nitrite, and metals have toxicity based on pH. Provided your water is pristine and devoid of ammonia and nitrite then large water changes should never cause any stress. Moving fish from water with low
TDS to high
TDS is often tolerated too, but moving a fish from high
TDS to low
TDS will often kill them in minutes. I never move fish from water with differing amounts of
TDS...never.
I have over 30+ years of doing this, with the last 8-9 years with planted tanks and the past 4-5 years with pressurized
CO2 injection.
