Bottom line: I think we can all agree now that the exact concentration of CO2 in a person's aquarium is pretty hard to know precisely. It probably isn't that meaningful when a person states that his/her CO2 is X ppm. There are significant errors in our ability to measure it, especially if you acknowledge the possible compounding effect of measuring mulitple variables with imprecise methods. There are probably significant errors in our understanding of the interactions of CO2 in a complex solution containing a mixture of many acids, organics, and buffers.
There are many issues that come into play when trying to defeat algae - CO2 is just one, albeit perhaps the most important. If there was a universal solution, someone would have figured it out a long time ago, and we'd all be following it now. There is no sense in being truly dogmatic about most anything we do since there are few things that we understand well enough.
It is perfectly reasonable to use as much CO2 as your fish can safely tollerate. Increase it until they show stress and back off a couple tenths. You need to be reasonably certain that your KH is stable if you are making decisions based on pH readings.
It seems reasonable that one could trust a relatively new, recently calibrated pH probe with more confidence than a bunch of hobby-grade KH/CO2/pH kit results. In the end, we're not trying to put a man on Mars or keep a patient alive in the ICU. This is a hobby, and there are plenty of other things to worry about too.
I'm getting the sense that the usefulness of this thread has just about run its course. If someone can find actual evidence that supports a better way to do this, please share it. I'd especially be interested in knowing if someone can accurately determine the resting equilibrium of CO2 in a buffered solution, or if they can determine if the actual KH affects the degassed CO2 concentration. |