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Information about Water Quality & Test Kits

Water Quality

There is a lot of talk about water quality when you are keeping fish. Your fish and other aquarium inhabitants need different water parameters.
e.g. Saltwater fish need a high pH and Tropical fish need a low pH.

Regular monitoring of water quality is essential. This is particularly so when the aquarium is first established. Testing the water will give you a better understanding of the aquarium water quality.

More information on aquarium ecology and the effects of ammonia, nitrite, and nitrate levels on aquarium water quality Opens in an External Site can be found on wikipedia.

Test Kits

Test Kits determine the concentration and levels of elements, compounds and chemicals in the water. See below for a table which test parameters suit what kind of aquarium.

Parameter Tank Type
Ammonia, Nitrate, Nitrite, pH Freshwater, Tropical, Marine, Reef
Calcium, Copper, Hardness, Iron, Phosphate Marine, Reef

What are some of these test parameters?

KH (Carbonate Hardness)

The KH of aquarium water should be tested frequently, since water with a low KH is subject to rapid shifts in pH, greatly stressing fish and making them vulnerable to disease. The kit measures carbonate and bicarbonate concentrations in the water. The proper KH level is an important part of water quality and is necessary for the health of fish and the development and growth of aquarium plants.


Ammonia in an aquarium can come from several sources including fish waste, uneaten food and other decaying matter. Ammonia is very harmful to fish. It will damage fish gills and prevent fish from carrying on normal breathing. Low levels of ammonia will stress fish, high levels will cause fish death.

Nitrate and Nitrite

Overfeeding, too many fish or inadequate biological filtration can lead to an unhealthy nitrite level. Nitrite in the aquarium interferes with fish respiration, and high levels of nitrite quickly lead to fish death. A high nitrate level causes poor water quality and increases the susceptibility of fish to disease.


pH is the measure of the aciditiy of water. In order for fish to thrive, it is important to maintain aquarium pH at a level similiar to their natural habitat. Most freshwater fish do best at a pH range of 6.8-7.5. Saltwater fish should be kept in a pH range of 8.2-8.4.


Copper, a common treatment for many parasitic infections, must be monitored carefully in an aquarium or a pond. The copper level can drop too low for the treatment to be effective, or can increase to a point that is detrimental to fish health. Copper my even be present in your tap water.


Calcium is one of the most important elements in a reef aquarium. Reef invertebrates such as corals, crustaceans, mollusks and even some types of encrusting algae need calcium to grow and remain healthy. The calcium level gradually drops in all reef aquariums as invertebrates utilise the calcium in the water.


Phosphate can enter aquarium through tap water, fish waste, and decaying organics such as uneaten food for dead algae. As phosphate increases so does your chance of having unsightly algae and green water blooms. In salt water, phosphate can also inhibit the growth of corals and other reef building organisms.

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