How (and How Often) to Test Aquarium Water for Healthy Fish and Plants

Regular water testing is vital for keeping tabs on the health of your aquarium fish and plants, but most beginners in the fishkeeping hobby are not aware of the importance of this practice. If the aquarium is “dirty-looking,” then people may clean the tank and do a water change. Aquarium water is actually made up of invisible waste chemicals that are derived from fish poop. These compounds can pose a danger if they are too high. Only test kits can accurately determine if the water is safe for fish and plants.

How to test water in a fish tank

Test strips are the most common type of water test for fishkeepers. Mixing a small amount of aquarium water with chemical reagent will change the color depending on the water parameter being measured. After a set amount of time, the reagent is compared to a color chart to tell you the final results. Here are the most common parameters we recommend looking at:

1. ammonia: ammonia is made by your fish or invertebrates using their waste. It is very toxic to animals, especially in water with high pH, and should stay at 0 ppm (parts per million). It can be measured using the Ammonia Test Strips.

Aquarium Co-Op Ammonia Test Strips

1. Nitrite In an older aquarium that has been cycled, beneficial bacteria eats the ammonia and makes nitrite. Nitrite can also be toxic to animals. It can cause severe burns to fish’s skin and gills. Keep it below 0 ppm. Multi-Test Strips can be used to measure it. 2. Nitrate A mature aquarium will have another type of beneficial bacteria that consumes nitrite to produce nitrate. This is less toxic for fish. As a general rule, we recommend keeping nitrate at 50 ppm or below. Aquarium plants consume nitrate as food so it is important to maintain a minimum of 20 ppm. To find out more, use Multi-Test Strips to measure it. 3. Chlorine Water from the municipal water supply is usually disinfected with chloramine or chlorine to remove pathogens. These chemicals are deadly to animals and must be removed from the water supply. To make sure your chlorine is at 0 ppm, measure it with Multi-Test Strips.

Aquarium Co-Op Multi-Test Strips

1. pH:PHP tells you how basic or acidic the water is. While most freshwater fish can survive at pH levels of 6.5 to 8.2, some species prefer pH levels that are lower or higher. Measure it with Multi-Test Strips or the API High Range pH Test Kit.

API pH Test with High Range

1. GH: The General Hardness (GH), which measures how hard or hard water is, is measured either in dGH or ppm. For freshwater aquariums, we recommend that you keep between 4-8 and 70-140ppm of minerals. It can be measured with Multi-Test Strips and the API GH & GH Test Kit Combo. 2. KH is Carbonate hardness (KH). This measures the water’s buffering ability. The higher the KH, the less likely the pH will rapidly change, which can be dangerous to fish. Like GH, it is measured in dKH (degrees of KH) or ppm, and we recommend keeping it at 3 dKH (50 ppm) or above for most freshwater aquariums to prevent pH swings. Measure it with Multi-Test Strips or the API GH & KH Test Kit Combo.

API H & KH Testing Kit Combo

1. phosphate: Phosphate (or phosphate) is a macronutrient which plants need to grow. But, excess phosphate can harm fish health and cause algae growth. Each aquarium is different and each fish and plant stocking levels are different. However, hobbyists recommend a minimum of 0.5-2 ppm for low-light tanks and 3 ppm for high-light aquariums that use CO2 injection. Use the API Phosphate Test Kit to measure it.

API Phosphate Test Kit

1. Copper – Invertebrates can be sensitive to trace amounts of copper in water. However, some medicines contain copper to treat specific fish diseases. The API Copper Test Kit can be used to determine the level of copper in tap water and to prescribe the right amount of copper-based medicine for sick fish.

API Copper Test Kit

1. CO2: If you are setting up a DIY or pressurized CO2 system, the Dennerle CO2 Quick Test is an easy and accurate way to measure the dissolved CO2 in your aquarium. Fill the prepared test tube halfway with tank water, shake for a few seconds, and immediately compare it to the color chart to see if you have too little, too much, or just the right amount of CO2.

Dennerle CO2 Quick Test

How often and when should you test your aquarium water?

Although water should be tested regularly, it is best to do so as frequently as possible. In the past, however, tests were costly and difficult to use. If fish keepers saw something odd in their tanks, they might ignore the problem and avoid testing the water because of these obstacles. Aquarium Co-Op test kits were created to be easier and less expensive so that you can test more often to ensure your peace of mind. These are some of the most common situations in which you should test your water.

1. New Aquarium When setting up a new fish tank, it takes a while to cycle the aquarium so that the biological filtration is mature enough to purify the water from your fish’s toxic waste. While the aquarium is cycling, it is important to frequently test the water on a daily basis to make sure the ammonia, nitrite, and nitrate levels do not get too high, so get the Ammonia Test Strips and Multi-Test Strips. If you get consistent safe and repeatable results, you can reduce testing to every three days. Then, test once a week. Finally, test once a month. You can read the full article about aquarium cycles.

1. Tank maintenance You may not need the Multi-Test Strips for your aquarium after it has been cycled. This is because nitrate can cause toxic reactions at high levels. We try to keep the nitrate level below 50ppm. If the nitrate reading is higher than 50 ppm or lower, then it’s time to change your water. In fact, one of the reasons why we keep live plants in our aquariums is because they help consume nitrate and thus can minimize the number of water changes we need to do. You can use our water chart flow diagram to determine how often water changes should be made based on your nitrate reading.

1. Sick Fish If your animals are displaying signs of illness or some are missing from the tank, it’s time to check every parameter possible to help you diagnose the issue. Begin by checking the water temperature and multi-test strips. Use the API High Range Acid pH Test Kit if you suspect an abnormal rise in pH. Copper is more toxic to invertebrates such as shrimps and snails. If you suspect that your water has changed, the API Copper Test Kit will help you test it. It is crucial to assess if the results are within a healthy range, and also to see if they differ from previous readings.

Fish health problems can arise from sudden changes in water parameters.

1. Unhealthy Plants When balancing the lighting and nutrients in a planted aquarium, nitrate is a key component to keep an eye on. Multi-Test Strips are used to measure the nitrate levels. It should be between 25-50ppm. If the nitrate level is lower than this, it might be time to add Easy Green all-in one fertilizer to replenish nutrients in the water. An overabundance or shortage in phosphate can cause problems like algae or leaves with large holes, so use the API Phosphate Test Kit to see what’s going on. Finally, if you are adding CO2 gas to the water to increase plant growth, get a read on how much dissolved CO2 is in the aquarium with the Dennerle CO2 Quick Test.

1. Outdoor Pond Large outdoor ponds that have large volumes of water should be tested at least three to five times per year with the Multi-Test Strips or Ammonia Test Strips. At the beginning of summer, we want to see how the water fared over the winter. In the middle of the summer, check the water quality because the fish have been eating different kinds of food and the pond evaporates faster in the warmer weather.

At the end of pond season, make sure all the water parameters are safe before preparing for the cold weather. Finally, it may be good to do an extra test in the middle of winter to see how the fish are doing.

Water test kits can be used for both aquariums and outdoor ponds.

The more mature and problem-free a fish tank is, the less frequently we tend to test it, but don’t forget that your aquarium is a living ecosystem and things are constantly changing. You should test your aquarium again if you travel, change fish food, buy or sell fish, add or remove plants or make other changes to the tank. In order to keep track of water parameter values over time, many hobbyists mark them down in a journal or computer spreadsheet. For a fish room with multiple tanks, our CEO Cory will mark the results down on blue painter’s tape and stick it directly on the aquarium glass.

To learn more about water chemistry, we’ve gathered a series of articles to help you increase your knowledge and enjoyment of the fishkeeping hobby. Check them out and enjoy nature daily!