pH is the measure of the acidity or alkalinity of the water in fish tank. The pH scale runs from 1 to 14. Where very acid water is 1 and very alkaline water is 14. Neutral water that is neither acid nor alkaline is 7. pH is logarithmic which means that every 1 degree increase or decrease is x 100 and 2 degree is already x 1000. Therefore, the importance of keeping pH in right level is the deference between life or death in the aquarium. Royal pH professional test will help to maintain your tank in the right level. With 120 tests in the range of 6-8.2, with very easy to read color chart, your fish will stay constantly in safe pH territory. It is always good to know what is the desired pH of various fish. The ideal pH value will lie between 7 and 8. However, African Cichlids from Lakes Malawi or Tanganyika require a pH higher than 8 whereas certain species from the Amazonian basin like Discus may prefer a much lower pH of around 6.2.