The Dennerle CO2 Long-Term Test Correct + pH enables the continuous, direct measuring of the CO2 contenct of the aquarium water. Conventional long-term CO2 tests are filled with a mixture of aquarium water and drop indicator. In contrast, the Dennerle CO2 long-term test Correct + pH employs a high-purity, ready-to-use ampoule indicator which has been developed especially by Dennerle.This offers the following key advantages:+ No additional measurement of carbonate hardness is necessary. Only a single colour-matching scale is required.+ The CO2 long-term test Correct +pH indicates the CO2 content correctly at all times - independently of other acids in the aquarium water (e.g. humic acids). Measuring accuracy now also remains unaffected by any changes in carbonate hardness as a result of increases in the hardness of the water, evaporation or water changing.+ The CO2 long-term test Correct allows direct determination of the CO2 content in millilgrams per litre - avoiding the need for addi