souffle (imo) you have it based on your last post.
Having the equipment here I've placed electronic pH controllers on low light NPT systems just to see what happens during a 24hr period. Lighting alone can shift tested pH by a full degree. Monitoring what the pH reading was in the morning before the photoperiod and again late in the afternoon I recorded a full point shift in value. The only difference was lights on or lights off (more or less CO2). Rapid shifts (swings) in GH, KH, TDS, (changes in osmotic pressure) that's what causes our critters issues not pH changes per say.
pH value is a product of carbonate buffers and CO2 content in the water for this conversation. Acidic or alkaline yes but testing pH as it relates to tank water and your question I agree with the answer you received, it really isn't anything to worry about.
As long as the temperature is matched I routinely swap fish between injected tanks with 5.9/6.2pH and 7.4/7.6pH low techs.
Temps the same, the TDS is very close and fish don't seem to care is why I support the position that CO2 induced swings don't matter.
When people say a fish requires a low pH I automatically read that as soft water.
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