[ray-the-pilot]

If you don’t have a CO2 controller there is no way to determine what the CO2 level is in your tank. Without a controller, the level will depend on the time of day, the location in your tank, the number quantity and health of plants and fish etc. These can result in a 100 fold variation in the level of CO2.

A drop checker only gives the approximate average CO2 level at one location and it does not control the level of CO2. It is really only a ballpark estimate under these conditions.

With a CO2 controller, the CO2 in your tank is always the same everywhere. There are no hot spots, dead spots, changes with plant and fish activity…no changes period. Now the average CO2 level at one location is the exact CO2 level for the whole tank.

BTW I haven’t calibrated my controller in 3 months and I know it is still OK.
Whenever I bump into my drop checker and knock it off the glass I clean and refill it. I clean and refill my drop checker more often than I calibrate my controller.