CO2 Art Drop Checker Solution is the pre-mixed indicator fluid that makes a CO₂ drop checker actually work. It's a 4 dKH reference solution combined with a bromothymol blue pH indicator — ready to use, with no mixing or measuring required. Paired with a drop checker, it gives you an at-a-glance read on your dissolved CO₂ level by simply changing color.
Good to Know — reading the colors: The solution shifts with CO₂: blue means too little CO₂, green is the target (roughly 30 ppm — the sweet spot that feeds plants without gassing your fish), and yellow means too much. The important detail is the 4 dKH reference — never fill a drop checker with tank water, because its buffers and KH throw the reading off. The known 4 dKH base is what makes the color trustworthy.
It pairs with any drop checker, including the Hygger CO2 Drop Checker and the CO2Art Drop Checker Kit we carry. Worth knowing it reacts slowly (it shows roughly an hour behind real time), so it's for dialing in a stable level rather than catching minute-to-minute swings.
How to Use: Fill the drop checker about 2/3 full with the solution (no tank water), invert it carefully, and mount it on the inside front glass so an air gap is trapped. Read the color after it equilibrates (allow an hour or more). Replace the solution about once a month, or whenever it stops reading accurately or picks up biofilm.
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