"Joe" wrote in message
. ..
I've seen in some places that CO2 levels above about 15-20ppm can be
harmful
to fish but I've also seen that you can go much higher without harming
fish
as long as the O2 content is adequate. I'm asking because I have
liquid
rock coming out of the tap, the KH is 15 degrees. I use a pH
controller and
I have it set for 7.5. I am getting ready to start stocking with fish
and I
want to be adding tetras and corys and other fish that prefer low pH.
How
high can I bring the CO2 without it being a problem for the fish?



A year or two ago I researched this via google and read various articles
written back many years ago as CO2 injection became a available option.
I even saw an article explaining in detail the biological function of
respiration within fish. From what I remember elevated levels of CO2 in
the water column also elevated the level in the bloodstream of the fish.
I suggest similar research via google and decide for yourself.