Ammonia – often in high concentrations can make the water look cloudy/hazy and is highly toxic to fish.
Nitrite – often called the silent killer, although not as lethal as Ammonia – water looks crystal clear, is still very damaging to fish health.
Nitrate – the product of healthy filtration system, not harmful to the fish themselves but in high quantities can affect their reproductive cycle.
pH – this test is for the acidity/alkalinity of the pond water, the pH scale runs from 1 -14 very acidic is 1 and very alkaline water is 14, neutral that is neither has a pH of 7. Ideal pH for a pond is between 7 and 8.