My bubble... you burst it
Great post, elwaine. I think like not realizing this will be exactly like when I hated using test kits (though I do like the test tube playing pretend scientist part), I need to have the drop checkers in front of me to see if there's any ideas to bounce back. Without the drop checkers and any experience I can only bounce ideas off you guys as thought experiments, but I hope you'll entertain it:
It is also interesting that lots of folks make mention of adding enough CO2 until they see green, then adding a little more until they see yellow green. Your points about seeing shades of green hits hard for me: I am terrible with colors. Extra tough is its not as if I can adjust CO2 in very small increments with my particular needle valve, wait a few hours, look at the color again, then remember what the color was a few hours ago. But a difference in color (say, from whats totally green to whats a weird yellow green) still sounds easier to see... I wonder if we could adjust our CO2 targets for that.
Anyway, if we run with elwaine's +/-.2 pH, this becomes much hairier since, for example, +/- .2 pH is -10 / + 20 ppm CO2 with 4dKH, but is - 15 / +25 ppm CO2 at 6dKH.
(I could add that CO2 margin of error to the calculator based on +/- .2pH off of the resulting dKH of the solution. Sure the .2 pH is an estimate, but as fort said all we're really doing is trying to make a smaller ballpark... What do you guys think?)
To type this out for myself and anyone else who may be wondering if they want to drop the ~$25 (using fort's eBay suggestion for two drop checkers plus the baking soda) or a little more from GreenLeaf:
Let's say I have a drop checker with 3dKH (23ppm CO2 target) and its green. It says I have ~15-35ppm CO2.
I have a second drop checker with 6dKH (45ppm CO2 target) and it is green. It says I have ~30-70ppm CO2.
I use both. Now I know I have 30-35ppm CO2.
(With a 4dKH sample, using the .2pH/color margin of error ballpark, you have between 20 and 50ppm CO2.)
Also, to clarify, the "Double Check" drop checker from Cal Aqua won't work. Maybe someone else makes a design that will work as one unit (instead of two drop checkers, because, you know, thats only going to lead to having to make another tank for the extra drop checker later...
).