elwaine said:
Next question: Is there a difference in plant growth if one gauges the levels of CO2 as being between 25 - 45 ppm vs 30 - 35 ppm?
I'm not really sure, but have guesses. For example, the 30ppm CO2 rule of thumb number came from a bunch of folks playing with what is now known as a (sometimes) unreliable measurement (the assumptions made in the KH/pH/CO2 formula) and breaking the old rule of 15-20ppm CO2, which such reliable sources as the APD and Krib (many of the same gurus who post today) used as the long standing benchmark. Wouldn't it be neat to find out with (hopefully) more accurate numbers, even in an amateur/hobbyist experiment with relatively cheap equipment and a little bit of time?
It just seems counter intuitive to use gross "Dump and Bump" fert schemes (aka, EI) - to avoid rate limiting values from developing - and then focus on tightening up CO2 dosing in order to achieve better plant growth. Anyone happy with EI should be happy with a single bubble drop checker with a 4 dKH solution and run their CO2 at a bubble count rate that turns the color in the bubble yellow green (not green). That way, CO2 would be closer to 45 ppm than 25 ppm and would not be rate limiting.
Yes, and this is EI wonderfully stated. But its easy to think of many questions spawned when one has a better guess about CO2:
If we can force green plants red via stressing them by limiting the second biggest macro nutrient (the low N brings reds method), what happens when we play with the biggest macro? (Also note lots of folks who use EI do it while setting maximum limits to control growth, or based on anecdotal experience, or whatever other reason.)
What if the amount of avaiable CO2 in a tank actually changes throughout the day in a way we can see, but currently can't because of the wide limits available to a hobbyist's most accurate measurement device (drop checkers). If I did set a 30-35ppm CO2 range, would I stay there all day, even in a presurized setup, or would I see my CO2 much higher in the day and night (lower uptake periods during the photoperiod)? Do I really only need that target as my minimum limit? Or are those periods even higher uptake at all? Will I even know since it takes so long for the gas to equalize?
How much CO2 am I pushing into a sunlit tank I feel good about on CO2 when I got there using the old "see algae or poor plants? Increase CO2. See fish gasping? Thats bad... lower CO2. Wait, need more CO2..." method?
*shrug* Dunno yet...
Thank you for your time and thoughts and expertise!