Adding further to this issue:
Light levels, nutrient limitations, plant biomass as well as species type etc can influence CO2 demand from plants.
Some might be okay with 15ppm of CO2 at 3 w/gal with a rug of HC in a well scaped iwugamiscape, whereas someone with a well lit dutch scape might require 30ppm etc.
While these may be minimum levels, the maximum levels tend to be defined by the fish, which if you set up the system correctly, can be at 30ppm, just because you happen to get away with less, does not mean you apply it to every case.
Some do so without consideration about plant biomass, light, and nutrients etc. Do not fall into that trap.
When addrssing CO2, it is likely best to eyeball how the plants grow best, but when you are sure that the plant biomass is consisent, flow, cleaned filters are present, good water changes, stable feeding, stable dosing of non limiting levels, then test the CO2.
The goal is use a combo, use all the methods available to you to measure CO2.
1.Plants growth/health/pearling/O2 levels
2. pH KH levels.........these maybe relative levels, level which you know work for your particular system having gone through the above routines.
3. More precise measures of pH/KH- drop checker is good here, however, thesre are some trade offs here, one is color resolution, some folks are color blind...............they cannot use this method without help.
4. pH drop checker take about 2 hours or so to equilibrate to the actual conditions in the tank.............
A tank can run "dry" of O2 in less than 1 hour.............
5. You can try various membranes and CO2 reference points and make a pH/KH reference pH probe+ a membrane, this a DIY project and getting a good bubble free seal, using a flat tipped pH probe are required.
You can buy a CO2 reference probe set up for about 500-700$ or so.
Not a small amount.
6. You may use very large back to back water changes to remove any peat or tannins in the tank water to get a reference measure of pH.
So you remove all the acids and replace with tap, then measure pH/KH and use that reference. as a baseline. You may also use RO water + baking soda to get a KH refernce if you suspect the tap water having non carbonate alklalinity as well.
From there, as long as the CO2 rate added is the same, and the plant biomass, KH, nutrients, light are similar, then the movement of the pH due to tap, due to tannins from wood etc, are not due to CO2.
So say the tank RO/Baking soda 90% water(2-3days in a row of this) changes is a pH of 6.4.
After awhile the tannins or peat drop it to 5.8.
You know that the CO2 is 30ppm at the reference, the new 5.8 is also at 30ppm as well, even though the pH/KH table now says it's 130ppm, but fish are fine and so are plants etc
Such back door common sense approaches allow a lot more used input than banter, they offer solutions and answers.
Seeing which trade offs work well for you is a key here.
I find that the plants are the best test kits as well as algae.
This simple method has never failed me.
I do test later............with a good hypothesis and decent method to test to see if it's true. But I do not test merely to monitor, I test on purpose driven question which teaches a lot more.
This method wor much better and reduces the work involved and answers questions rather than repeating history over and over again and the same associated myths.
Reinventing the wheel gets old
I think many can agree on that.
The drop checker is not reinventing, yet the idea is very old, at least 25 years old. Adding the KH ref solution is somewhat new. Combining good justitifications for them(This part maybe new) is a step closer to being better for the future hobbyists.
Regards,
Tom Barr
