this is the header for the print friendly version

Pet Aquarium - Everything For Your Pets and Aquariums

Home | Links

Aquarium Information

Water Quality

 The water in the tank has never looked clearer, the pH of the water is right on 7.0, but the fish just don't seem healthy. One or two die every now and then and their colours just don't seem as bright. Does this sound familiar to you? Certainly the pH of the water is one of the most important factors of water quality, but there are at least eight other factors that effect not only the health of the fish, but their colour, their growth rate and their ability to breed. In this article we will look at some of the most basic parts of the chemistry of your water and what effect each has on your fish.

Table of Contents:

Click on the links below to take you to the information you require



The pH of the water is different in different waterways of the world for a variety reasons. This means that fish from the Amazon will more likely have a different pH than Australian Natives. Fortunately for us most fish are happy to live a pH of 7.0 and that means we can have a nice mix of fish from all over the world in our tank. If the pH of the water is not neutral, then it's either acid or alkaline. To measure this, use a pH test kit. These are very easy to use and are quick and accurate. If the pH of the water is too acid or alkaline then fish come under heavy stress, and we know that when fish are stressed they can pick up a disease. 

When to Check it? Generally pH should be checked once per week. If the pH needs to be adjusted, re-test after 24 hours.

Top of page

Ammonia / Nitrite / Nitrate 

Ammonia is caused by the breaking down of waste products in your tank. This waste includes uneaten food, fish waste, dying plants; and the fish themselves also excrete ammonia out their gills. Fortunately, there are bacteria that eat this ammonia and turn it into nitrite. A different bacteria strain converts this Nitrite into Nitrate, and we generally dilute these Nitrates in the water when we undertake a patial water change. Both Ammonia and Nitrite will occur in the water if there is not enough bacteria to cope with the amount of waste which is why we encourage customers to purchase fish slowly and ensure all food given to thr fish is consumedwithin 30 seconds to 1 minute. Ammonia is deadly and will kill fish in some cases within an hour or two.

When to Check it? Ammonia should be checked whenever a new tank is set up, when new fish are added, or 24 - 48 hours after the filter is cleaned.

Carbonate Hardness

If the pH of your water keeps going acid no matter how much 'pH Up' you use, then you more than likely have a low Carbonate Hardness or kH. When a high kH is maintained, the pH will stay stable and will then rarely fall. As the pH of the water becomes more acid, the kH decreases making the pH unstable, also stunting the growth of plants. kH can be easily increased using Carbonate Hardness Generator and Carbonate Hardness Test Kit.

When to Check it? Carbonate Hardness should be checked every week and adjusted until the desired levels are reached. Monthly testing is then sufficient.

Top of page

General Hardness

Firstly, General Hardness has nothing to do with Carbonate Hardness. It is actually a measurement of the amount of dissolved minerals and calcium in the water. General Hardness effects fish and plants by restricting growth and colour, and it will also stop the fish from breeding. If you are using a water conditioner appropriate to your fish and doing regular water changes, then Hardness should not be a problem for your fish.

When to Check it? If you are planning to breed or grow baby fish, then hardness should be checked weekly.


If you've got an algae problem in your pond or tank, then its very likely that you have high levels of phosphate in the water. Although phosphate has no direct effect on fish, it does feed algae, and this can starve the water of oxygen which in turn can kill your fish. Phosphate comes from certain types of food, waste and even some carbons. If levels are high, it can be removed by using a Phosphate Sponge and by reducing waste levels. (Especially excess food)

When to Check it? In freshwater, check the phosphate whenever major algae problems arise.  If you have live coral, phosphate should be checked weekly. When testing for phosphate, also check the tap water as this can be a source of phosphate in the tank.

Top of page


Calcium will only need to be tested if you are keeping corals in a saltwater reef aquarium. Calcium should be tested weekly or before supplements are added.






Salinity is the measure of salt in the water and is most commenly checked with a hydrometer or refractometer. It is only used for saltwater aquariums and should be tested weekly. Incorrect levels of salt will affect the fishes ability to osmoregulate. The most common salt problem that people have is not topping up with fresh water when water evaporates, hence salinity will rise over time.

 Top of page

Special Notes

There are other chemicals and nutrients in the water that we can test for, but these are the most common elements that will effect your aquarium environment, and the health of your fish. With this in mind what kits do you really need?

Freshwater: Every freshwater fish keeper should have a pH kit, Ammonia kit and a kH kit. If you're planning on breeding, then add a General Hardness kit, and if you've got any issues with algae then a Phosphate kit will often assist you.

Saltwater: Saltwater aquarists should keep a high range pH test kit, KH test kit, ammonia test kit, Nitrite test kit. If corals are kept in the aquarium you will also require Calcium test kit, Nitrate test kit and Phosphate test kit.

One quick note about test kits - the indicators in them usually only have life of about 12 months. After that time they can give inaccurate reading so check how old your indicator is today. Remember its the quality of the water that effects the health of your fish, and we know that poor water quality leads to stress, disease and ultimately death. By testing the water yourself, it helps you understand your water better and helps you to head off any problems before they become too dangerous.

A list of ideal water parameter are as follows:

               Goldfish  Tropical  Cichlid  Marine  Reef
 Ammonia  0 0 0 0 0
 Nitrite  0 0 0
 Nitrate  0
 pH  7.0 - 7.4  6.8 - 7.2  8.0 - 9.0  8.1 - 8.4 8.1 - 8.4 
 Carbonate Hardness  40 - 60 ppm  40 - 60  80 - 200  120 - 180 120 - 180 
 General Hardness  150 - 300 ppm  60 - 150  60 - 400  N / A N / A 
 Phosphate  <1 ppm  <0.5  <1 ppm  <0.5 <0.5 
 Calcium  N / A  N / A  N / A  N / A 375 - 450 ppm 
 Salinity  N / A  N / A  N / A

 1.002 - 1.024 

(30 - 35g/l)

 1.022 - 1.024

(30 - 35g/l)

Top of page