General Hardness (GH) in an aquarium refers to the concentration of dissolved minerals, primarily calcium and magnesium ions. A high level indicates an abundance of these minerals, potentially detrimental to certain fish species and aquatic plants that thrive in softer water conditions. For instance, some South American fish, like tetras, prefer softer, more acidic water parameters.
Maintaining appropriate water parameters is crucial for the health and well-being of aquarium inhabitants. Controlled mineral content promotes optimal physiological function, reducing stress and susceptibility to disease. Historically, aquarists have employed various methods to adjust water hardness based on the specific needs of the aquatic ecosystem they aim to create.