The key to having healthy fish is maintaining proper water chemistry. This Article covers everything you need to know about the following:

Chlorine and Chloramine, Slime Coat Protection, pH Levels, Ammonia, Water Hardness, Nitrites and Nitrates, Buffering Capacity (Alkalinity), Salinity, and Temperature

The most important thing to remember about water chemistry is to provide a constant environment for your fish. Fish are harmed more by rapid fluctuations in pH, temperature, etc. than by any other hazard.

Best Water For Fish Tank. How to Add Water to Fish Tank

Most fishkeepers rely on water from the faucet when setting up an aquarium or when doing a partial water change. City water departments add many chemicals such as chlorine and chloramine to tap water to kill bacteria (good and bad bacteria). Because these chemicals are deadly to fish, never keep fish in untreated tap water! Fill the aquarium with water, treat it, and then add fish once the water is stabilized. After doing a partial water change, the water in the aquarium will again need to be treated to insure that the chlorine or chloramines have been neutralized. 

How often to change water in fish tank?

You should change 20% of the water in your fish tank every two weeks. After filling up the fish tank, it is important to note that you should never replace all the water in a fish tank for cleaning purposes.

Chlorine and Chloramine Removal Aquarium

Chlorine is found in most tap water and must be neutralized with a water treatment that removes chlorine.

Chloramine is a combination of chlorine and ammonia. It is a stronger disinfectant than chlorine alone and is used in areas where this extra disinfection is needed. You can call your local water department to find out if chlorine and chloramine is in the water, or you can buy a Chloramine/Chlorine test kit. It is important to remove chloramine from you aquarium immedietly if detected.

These chemicals must be neutralized with a water treatment that removes chlorine and chloramine. Water with chlorine and chloramine in it must be treated with a product that will neutralize both chemicals. Here is a link to the best chlorine remover for fish tank.

Fish Slime Coat

When fish are moved from aquarium to aquarium, or they are in a weakened condition from transporting, their stress is increased and their protective slime coating may be lost. A slime coat product should be used in conjunction with chlorine/chloramine removers to help reduce stress and provide a protective slime coat on the fish that is sometimes lost.

pH Levels (Fish tank water test kit)

pH is the measure of how acidic or alkaline the water is. pH levels should be monitored weekly and adjusted to suit the fish. Most tropical fish can live happily in a range of pH values — from 6.8 to 7.8. It is critical however, to maintain a stable pH level in your tank.

There are kits available to test the pH level. Products are available to bring the pH up or down as needed. Home test kits with pH adjusters are also available.

How to Reduce Ammonia in Fish Tank

Ammonia poisoning, the leading cause of fish loss, is most likely to occur at toxic levels in a newly established tank where the process of biological filtration has not been established, in an old aquarium where the pH has become alkaline, or in an over-crowded tank.

Ammonia, which destroys the mucus membranes of fish, is secreted by fish directly through the gills as a waste product, and by the bacterial breakdown of fish waste, uneaten food and plant by-products. This causes the ammonia levels in the tank to reach toxic levels, known as ammonia poisoning.

Adequate and proper filtration, and regular water testing, help keep toxic ammonia levels from occurring. Products are also available to help keep ammonia levels in check. Ammonia can be removed by using a liquid ammonia remover that is placed directly in the water, or ammonia chips, which are put into your canister or power filter. Fun Fact: some fish tank ammonia removers can be used for cloth diapers (the more you know!)

Hard Water in Fish Tank

Water hardness refers to the amount of calcium and magnesium salts present in the water. If your water is too hard, and can cause white crust to form in and around the aquarium. Hard water makes it difficult to adjust the pH. Products are available for water softener for fish tank at Walmart.com

Nitrites and Nitrates

Nitrites are converted by beneficial bacteria into nitrates. High levels of nitrites indicate that the breakdown of organic materials isn’t complete and that the aquarium does not have adequate biological filtration. Nitrites are less toxic than ammonia, but can still kill fish if the levels are too high. Nitrates, on the other hand, are generally harmless to freshwater fish and are actually used by plants and algae as food. Test kits are available that test the levels of both nitrites and nitrates.

Aquarium Alkalinity

Sudden changes in pH are very stressful to fish. Water without the proper level of buffering capacity (alkalinity) is very susceptible to changes in pH. Properly buffered water has a 120 to 240 parts per million (ppm) total alkalinity reading. You can buy products that will increase the buffering capacity of your aquarium water.

Salinity of Aquarium

Most people think that salt only belongs in salt water aquariums, but this is not always the case. Freshwater fish tanks can actually benefit from small doses of salt. In fact, a low level of sodium (salt) can actually break down the fish’s slime protective coating. One tablespoon per five gallons will provide enough salt for most fish. Mollies, Swordtails, Tetras, Fancy Guppies, and Goldfish prefer a little more. Cichlids, Knifefish, and Ghosts prefer less. Only use salt that is recommended for aquariums. Never use regular table salt which may contain iodine.

Fish Tank Water Temp.

Freshwater tropical fish must have a stable water temperature within the range of 75 to 82 degrees Fahrenheit. Fluctuating water temperature causes stress on the fish. It is always a good idea to buy a good quality aquarium heater and a floating thermometer to help you regulate your water temperature. In most homes you need to maintain the minimum temperature. Don’t forget your fish when you leave your home for extended periods of time. Check the operation of your aquarium heater in winter and remember if you turn off your air conditioning in summer, the temperature in your aquarium may get too high.