Goldfish Water

In order to keep goldfish happy and healthy, there are a few water-quality parameters that you must be aware of: water hardness, pH, and nitrogen . Before you place your goldfish in the aquarium, make sure to test the water.


goldfish bowl



The amount of dissolved mineral salts , namely calcium and magnesium, will determine the water's hardness. Water with high concentrations of salts is referred to as hard, while low levels would be indicative of soft water. Hardness is measured with the degrees of hardness scale (dH), which ranges from 0 to over 30 degrees, with 4 to 8 degrees reflecting soft water and 18 to 30 degrees reflecting hard water. This can also be expressed in parts per million- soft water is less than 75ppm and hard water is within 150ppm to 300ppm.

Goldfish prefer water hardness between 3 and 14 degrees of hardness. Eventhough goldfish can survive in water with a higher hardness, commercial kits are available at pet stores that will allow you to alter the water hardness, so there is no need to gamble with the health of your pet fish.




The amount of acidity in the water is referred to as pH. The pH scale ranges from 0 to 14 with a pH of 7 being neutral, a Ph of 1 being very acidic and a pH of 14 being very alkaline. This scale is logarithmic , meaning that each number is ten times stronger than the preceding number. For example, a pH of 2 is ten times more acidic than a pH of 3 and 10 times more acidic than a pH of 4.

The acidity of water, and hence its pH , is influenced by a variety of factors that include the amount of carbon dioxide and fish wastes in the water. In general, goldfish and koi are quite tolerant of various pH levels. Commercial pH test kits are very simple to use and available at most pet stores. This water parameter should be monitored every week or two to detect any changes. Whenever possible , the pH should be maintained between 6.8 and 8.0, and great fluctuatiions should be avoided. An abrupt drop in pH may be indicative of an increase in carbon dioxide or fish wastes. An increase in aeration or a partial water change may help to alleviate the problem.




Goldfish and koi , like all fish, are living creatures that obtain energy from food and burn that energy with the help of oxygen, which they breathe from the water. However, these processes generate waste products that are returned to the environment via the gills and the digestive system. These wastes are primarily carbon dioxide and nitrogenous compounds such as ammonia. In the aquarium, these wastes must be removed. Carbon dioxide generally leaves the water through aeration at the surface or through photosynthesis by aquarium plants. Toxic nitrogenous compounds are converted to less toxic compounds via the nitrogen cycle.

In nature, the nitrogen cycle involves the conversion of toxic nitrogenous wastes and ammonia into harmless products by bacterial colonies.

nitrogen cycle

In short, bacteria drive the nitrogen cycle as they convert solid wastes and other organic debris (uneaten food) into ammonia, ammonia into nitrite, and nitrite into nitrate. Nitrate is then used by plants as fertilizer and is removed from the water. A healthy aquarium depends greatly on the nitrogen cycle to reduce toxic ammonia into less toxic nitrogen compounds. When setting up a new aquarium, it is important to measure these compounds every week for the first couple of months. After this period, once a month is sufficient, unless you suspect a problem. You should see ammonia increase first, then decline as nitrite begins to elevate. As your bacteria colony flourishes, nitrite will decline as it is converted into nitrate, which increases slowly. Plants and frequent water changes will remove nitrate before it reaches toxic levels.

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