Simple definition: General Hardness (GH) measures the concentration of dissolved minerals, mainly calcium and magnesium, in pond water.
Detailed Explanation
‘Hard’ water has more dissolved minerals, ‘soft’ water has fewer. Different fish species tolerate different hardness ranges, and hardness also affects how stable a pond’s pH stays over time.
Why It Matters
Very soft water gives pH less buffering, so it can swing sharply with small changes, stressing fish. Hardness is often overlooked compared to pH and ammonia, but it affects both.
Practical Example
A pond topped up mostly with rainwater will trend softer over time than one topped up with tap or well water.
Related Terms
pH
