JBL ProAquaTest KH Carbonate Hardness, Refill

The JBL ProAqua Test KH is a water test for analyzing the optimal carbonate hardness in freshwater and seawater aquariums, as well as in ponds.

Depending on the origin of water, e.g. due to the nature of the substrate, different levels of different mineral salts, carbonates and carbon dioxide (CO2) form an important buffer system that prevents dangerously high pH fluctuations in the water. The measured carbonate hardness (KH) gives the total concentration of bicarbonate in the water and therefore may in rare cases (when mainly alkali bicarbonates are present, such as in East African lakes) be higher than the total hardness when considering only alkaline earth salts. Most freshwater fish and plants in the aquarium can be maintained successfully with a carbonate hardness of about 5-16 ° dH. However, for optimum CO2 fertilization, the carbonate hardness should not be below 5 ° dH. In the case of CO2 deficiency, aquatic plants or algae consume hydrogen carbonate (bio-decalcification) due to their rapid assimilation during photosynthesis and can thus dangerously raise the pH value for fish (over 10).

Recommended KH values:
Freshwater aquariums (community pool): 5-12 ° dKH
Malawi Lake Tanganyika Aquarium: 7-20 ° dKH
Plant aquariums with few fish (aquascaping): 3-8 ° dKH
Marine aquariums: 7-10 ° dKH
Ponds: 7-10 ° dKH

Our expert Oliver Knott recommends:
The carbonate hardness is crucial for the buffer capacity in the water and affects the pH value - a regular check is therefore essential!