Measure and add context
Record the baseline and check GH as dissolved calcium and magnesium. Do not infer the aquarium's condition from a single sign. Record method, time, temperature and recent changes so the reading can be compared.
Then compare KH as buffering capacity against acid with livestock needs and recent changes. Assess the trend alongside breathing, behaviour and species requirements.
Correct without destabilising
Adjust one variable and assess osmoregulation, plant and stability requirements before continuing. Keep a reference so the result can be compared. Address exposure or cause first, then retest before stacking products or interventions.
GH and KH degrees are not interchangeable even when both are called hardness.