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Testing aquarium water is a key component of maintaining a healthy environment for fish. The question is, what should be tested?
"The must-haves to test for are pH, ammonia, nitrite, and nitrate," says Nic Tiemens, co-founder of Infinity Aquarium Design. "I would say that all good aquarists test their aquariums on a regular basis for all of those. Anytime you are dealing with live animals the more you can do for them, the better."
This list of aquarium water test kits helps sort what to test for and provides information about what testing products are available.
Master Test Kits
Combination, or Master test kits are touted as the perfect way to have all the tests you need on hand. But are they worth the money? The pros of buying a combo kit are lower cost per test, everything has the same expiration dates, and it’s a quick and easy way to purchase and keep the basic tests all at once.
The downside is that one can’t customize tests; the components within the kits are fixed by the manufacturer. Another complaint many have is that, much like the printer ink cartridges that come bundled together rather than purchased separately, the kits tend to run out of one component long before the others.
What should be done? It is recommended to get a master test kit with at least pH, ammonia, nitrite, and nitrate. Other components in the kit may vary by manufacturer, and select the one that has the most other tests that you would use. Selections are chlorine, chloramine, hardness, alkalinity, phosphate, iron, copper, calcium, and possibly other tests. The kit may contain chemicals in the form of tablets. liquids and some include test strips.
Ammonia Test Kits
An ammonia test kit is one of the must-haves for every aquarium owner. However, not all ammonia tests are created equal. The primary issue at hand is the fact that ammonia can be present in a non-ionized form (NH3), or the ionized form (NH4+) known as ammonium.
The toxic NH3 is what hobbyists are concerned about, but most tests give results for the total of NH3 and NH4+, the total ammonia-nitrogen value. The difference can be determined by using an Ammonia Ionization Chart, when you know the aquarium water temperature and pH. The toxic ammonia level (NH3) should always be at zero, but sometimes there will be the non-toxic ionized form (NH4+) of ammonium present in the aquarium water.
Seachem kits reliably test for both total ammonia and NH3, however, the kits cost more than the type that tests only for total ammonia. Seachem also produces ammonia alert products that are placed within the aquarium to indicate ammonia level, which are generally good but are not as reliable as actual test kits.
Nitrite Test Kit
Nitrite is another test that is important during the start-up of a new aquarium, as well as for ongoing water analysis to catch problems before they become serious. New aquariums should have the ammonia and nitrite levels tested at least weekly to prevent the problem called "New Tank Syndrome." Once you have your aquarium well-established, we recommend testing for nitrite monthly and any time a fish is sick or dies.
It is preferable to use liquid test kits for accuracy, but using test strips will give a general guide to the nitrite level, which should be at zero. If any nitrite is detected in the aquarium water, steps should be taken to remove it.
It is common to see combo test strips of nitrite and nitrate, and other tests all on one plastic strip. However, the chemicals to test ammonia may affect the nitrite and nitrate testing, so ammonia is usually on a strip by itself.
Nitrate Test Kits
Nitrate is not as dangerous for fish, but at high levels it stresses them, leaving them more susceptible to disease and ultimately shortening their lifespan. If it is desired to breed fish, keeping nitrate low is a must. Elevated nitrate is also a major contributor to algae growth. For all those reasons, it’s wise to track nitrate levels regularly in any aquarium.
While ammonia and nitrite levels should always be at or near zero (0.0 milligrams per liter, mg/L) in the aquarium water, nitrate can go up to 10 or even 20 mg/L (also measured as parts per million, or PPM), it is important to do partial water changes to lower the nitrate if it gets to 40 mg/L or more.
Nitrate tests are often included in a master test kit or paired with a nitrite test kit, but they can also be purchased separately. As with other tests, liquid test kits are preferred. However, if cost is an issue, the strips will do. They are not as accurate as using a liquid or tablet test, but will give a general range that is close enough to take action if the levels are high.
pH Test Kits
The pH (acid-base balance of a solution) is a key parameter for all aquariums and should be tested and recorded in a log on an ongoing basis. Sudden changes in pH are often the invisible cause of fish disease and death. Gradual pH changes are less serious in the short term, but ultimately can be just as dangerous to the health of fish as a sudden pH change.
If using strips instead of liquid test kits, take care to reseal the container of strips tightly and don’t touch the pads on the strips with dirty fingers. For more accuracy, electronic pH meters are available in a variety of sizes and prices, and are a great investment for an avid aquarist. The electronic meters must be calibrated periodically, and standard pH solutions are available to use to test and adjust the meter readings.
Hardness and Alkalinity Test Kits
Hardness and alkalinity, which refer to the levels of dissolved minerals in the water, are useful tests. Hardness measures the positive ions (cations) of calcium and magnesium, while alkalinity measures the negative ions (anions) of carbonate and bicarbonate, among other lesser minerals. The hardness is sometimes referred to as General Hardness (GH), and the alkalinity might be referred to as Carbonate Hardness (KH). In German, the word for carbonate is spelled with a K and that is where the term KH for alkalinity originated.
Alkalinity (KH) has a direct impact on the stability of pH, which affects the species of fish that will thrive in the tank, as well as being necessary for the beneficial bacteria in the biofilter that detoxify wastes, making it an important parameter to assess periodically. The higher the KH, the more stable the pH will be.
Hardness (GH) measures whether the water is hard or soft. GH should be matched to the species of fish being kept. For instance, Tetras do best in softer water, while most African Cichlids thrive in hard water. GH is particularly important when breeding fish.
Phosphate Test Kits
Generally, this test is most often used in saltwater aquariums. Phosphate is not a commonly used test in freshwater aquariums, as elevated levels will not harm the fish. However, phosphate is a key factor in algae growth. If battling algae problems, knowing the phosphate level can help determine if the steps being taken to lower the phosphate levels are having the desired effect.
Phosphate can be introduced into the aquarium through fish foods, as well as through your local tap water. If you detect high phosphate in the aquarium, water changes may help, unless your local tap water is also high in phosphate. Be sure to measure the tap water, or call your local water company to see if the tap water contains phosphate.
Oxygen Test Kit
Oxygen is rarely tested in home aquariums, but there are special situations where it is useful. Densely populated tanks, such as those that breeders might have, or densely planted tanks are two situations in which oxygen levels may require closer examination. Both salinity and temperature impact the amount of oxygen that can be dissolved in the water. Warm water holds less oxygen than cold water, and freshwater holds more oxygen than saltwater.
In addition to a liquid test kit for measuring oxygen, electronic meters are available to test for dissolved oxygen. Most oxygen meters will also test the water temperature and calculate the percent of oxygen saturation. As the dissolved oxygen level will decrease with higher water temperatures, you want to know not only how much oxygen is in the water, but if it is at saturation. If it is, then the oxygen level is perfect. Adding more oxygen can cause supersaturation, which causes gas-bubble-disease in the fish.
Iron Test Kits
Iron is present in trace amounts in aquarium water and generally does not require testing. However, plants require iron to thrive, and those who keep heavily planted tanks, or propagate plants, may test the iron level. There are commercial iron supplements available for planted aquariums, and iron test kits will help determine how much to add to the aquarium.
Copper Test Kits
Copper tests are needed when copper-containing medications are used to treat sick fish. Testing for copper allows for accurate dosing of the aquarium water when giving copper treatments. Some tap water may also contain copper at high levels, especially in facilities that use copper pipes. Fish vary in sensitivity to copper, and copper is removed from the water by the fish and stored in their bodies, so copper can have a cumulative effect and become toxic to the fish in water that constantly has even a low level of copper.
If you're looking to make one simple purchase that covers all your testing needs, consider picking up a master test kit (view on Chewy).
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This roundup was written by Shirlie Sharpe, fish expert and author of the book Knack Aquariums: A Step-by-Step Guide to Raising Healthy, Beautiful Fish.
For additional background on aquarium water test kits, we interviewed Nic Tiemens, co-founder of Infinity Aquarium Design, who spoke about what water test kits are essential.