Review on Level Up Your Aquarium: The U.P. Aqua Co2 Indicator Unveiled by Julie Johnson

Pros: They actually give you the overall pH after slowly adjusting. Monitor pH constantly enough to know if it's too low or too high. hours) to react sufficiently to provide the overall pH. --- The CO2 indicator liquid they sell you is very expensive when you buy it in those little dropper bottles. The liquid looks and reacts to water as if it were bromothymol blue, which measures a pH of around 7. So I use BTB as this indicator and it does its job cheaply - incrementally. Do not install in direct sunlight as algae will grow faster. on topic. This is an accessory that will help you, but is not required for a freshwater aquarium (if you have another way of measuring pH).