First, off, Nice looking tank, and discus. I see your Harlequin Rasboras don't tend to school either.
Can there be an excessive amount of c02 in the tank as measured by my drop checker, as long as the plants are producing enough o2 as indicated by massive pearling? Does it work that way?
OK, I hope I get this right I'm a programmer, not a biologist, but here is how I understand it:
Yes, you can still suffocate a fish if you have tons of Oxygen in the water, but the CO2 level is too high.
CO2 will exit the fish's blood stream via the gills trying to get from a higher concentration area (the blood) to a lower concentration area (the surrounding water).
If the water contains very High levels of CO2, the fish will not be able to "breathe out" so to speak.
found an interesting article here:
The effect of increased CO2 in water is to reduce the rate at which CO2 from the fish's own metabolism can be released from the blood through the gills, thus the CO2 in the blood also increases - this is known as hypercapnia - resulting in a drop in the blood pH, an acidosis. At the same time the oxygen-carrying ability of the haemoglobin in the blood is reduced.
BTW, I would love confirmation from a real biologist or just a generally smarter person, so I know if I can say this again.