Carbonate hardness (KH), also known as alkalinity, represents the buffering capacity of aquarium water, its ability to resist changes in pH. Insufficient KH can lead to rapid and potentially harmful pH swings that stress aquatic life. Stable water parameters are essential for a healthy aquarium ecosystem. For example, if KH drops too low, the addition of even a small amount of acid (naturally produced by biological processes) can drastically lower the pH, potentially causing fish death.
Maintaining adequate alkalinity is crucial for biological stability within a closed aquatic environment. It supports the nitrification process, where beneficial bacteria convert toxic ammonia into less harmful nitrates. A stable KH value contributes to the overall health and resilience of the aquarium inhabitants, protecting them from the negative effects of fluctuating pH levels. Historically, aquarists have recognized alkalinity as a cornerstone of responsible aquarium management, employing various methods to maintain it within optimal ranges.