Estimating Co2 Levels


New Member
Oct 27, 2019
New England, USA
Hi everyone! I need some help gauging CO2 levels in my new tank; I've heard conflicting reports on how to do so and thought this would be a good place to come for advice. Here are some details on the tank (forgive me...this is a lot);

- The tank - a standard 5.5 gallon (or roughly 20 liters) - has a drop checker which is deep yellow. It does not currently have either light nor plant nor livestock.
- The tank has a PH of 5.5 and a KH of 3 degrees. Inputting this value into a typical CO2 calculator implies over 280 ppm (!) of CO2...I am assuming that is off...
- If allowed to off gas, the tank's water acquires a PH of about 6.8.
- I am using a 1 liter yeast reactor with about 1 cup/237 ml raw sugar, 2.5 ml yeast, 1.25 ml corn starch, .625 ml baking soda, a fish food pellet, and about a liter of dechlorinated water (technically slightly less...a quart). The reactor is being heated to about 25.55 celsius/78 fahrenheit for consistency. This setup began producing enough pressure to push a mist through a ceramic diffuser a little over a day after I set it up, and the filter is keeping almost all of that mist in the tank.
- The filter does about 300 liters per hour and has an outlet about 1.5 cm above the water surface, so surface agitation is vigorous. Will likely need to tone down the filter when it is time to add livestock...
- The tank has a bubble counter, but it isn't working properly (I could not open it to fill it with water). I purchased a new one today so I can keep better track of how much CO2 is entering the tank.

How should I estimate CO2 levels in this tank? I've heard virtually all methods of doing so be criticized by someone, and I don't want to risk gassing livestock out when the tank is finally ready for an animal (probably my Betta smaragdina, Azure). Thanks :)