John van der Pflum wrote:

What happens is the the pressure in my CO2 tank drops over time
because obviously the CO2 is being released into the water for my
plants. The regulator I have on my tank cannot adequately control the
pressure when it gets too low and will all of the sudden just start
letting all the remaining CO2 into the tank.

The result of that is the PH crashes -- sometimes at or below 5 -- and
my fish get very stressed, needles to say. I have lost a few fish to
this problem.

A pH of 5? So we could be talking CO2 levels in the hundreds of ppm?
Almost atmospheric levels. It's amazing that any of your fish survived!

Nikki