Ph swing and what is dangerous

[JackBlasto]

I have a 100 gallon planted tank. Injected CO2. What is the acceptable swing of ph between day and night that won't harm your fish. I've read 0.4 as long as its gradual is ok. Anyone have two cents to add on this? I've yet to add fish to my tank while I get everything as natural as possible. I don't want my ph to shift so much it harms anyone. Also a side note... The co2 definitely affects the ph by almost an entire point so when I introduce water from my reservoir at 7ph it drops to 6 in the tank. I'm curious how adding water in water changes could negatively affect my fish life as well because of this. I realize adding small amounts is ideal but should I be worried about this at let's say 40% water changes? Thanks for any advice here.

 

[JackBlasto]

I just read that ph swings caused by CO2 don't affect fish!? Is this correct?

 

[JackBlasto]

I just read that ph swings caused by CO2 don't affect fish!? Is this correct?

And this is what I have come to conclude by reading other threads on other forums etc. PLEASE correct me if I'm coming to an incorrect conclusion here...

Its actually kh changes that affect the fish, not ph... Most people see the result of kh in ph and thus they commonly think that ph changes are bad for fish. With co2 it doesn't affect kh thus why it can change the ph of the water safely. Ph is changing but its not a bad change whereas if the kh of the water was changing (as in another variable causing the ph to change) it would be bad. Co2 doesn't change kh Thus CO2 affecting ph is a safe change in ph