No fish losses, I've actually never lost a fish to CO2.
Gassed a few good in the past, but they all lived.

Amano has killed many fish with CO2. He freely admits it.
pH controller got some at least once in his case.
Same deal with me but I caught it first and tossed the pH controller after that and will never use one again.

Generally the end of tank dumps apply to non needle valved systems.
Dave Gomberg use tio suggest a needle valve was not needed and sold Ehiem diffusers and reg's with no needle valve. Folks did fine till they got near the end of the tank and needle valve acted as choke to reduce the variation, but without one, many folks lost their entire livestocks due to this.
Dave's killed more fish with CO2 than many.

But now we know and adding a needle vale in conjuction solves the death issue with fish, but we still have a lower and lower CO2 rate and less CO2 in the start of lighting cycle, so it's a problem, but with plant growth and algae instead of dead fish.

I can get rid of algae and bring plant growth back, I cannot reainmate fish

Regards,
Tom Barr