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. The aquarium may need to be cleaned if it looks “dirty”. Aquarium water can contain invisible waste chemicals, such as fish poop, and other compounds that could be harmful at dangerous levels. Only test kits can accurately determine if the water is safe for fish and plants.
How to test water in a fish tank
There are two types of water testing that fishkeepers can use: (1) test strips and (2) kits that include test tubes or small containers. 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 created by your fish and other invertebrates through their waste. It can be very toxic to animals in high pH water. The recommended level should be 0 parts per million. Measure it with 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 is also toxic to animals and can burn fish gills and skin, so keep it at 0 ppm. Use Multi-Test Strips to measure it. 2. Nitrate: In a mature aquarium, another type of beneficial bacteria consumes nitrite and produces nitrate, which is less toxic to fish. We recommend that nitrate levels are kept below 50 ppm as a rule. Aquarium plants consume nitrate as food so it is important to maintain a minimum of 20 ppm. It can be measured with Multi-Test Strips. Read our article on nitrate to find out more. 3. Chlorine Drinking water from municipal water supplies is most likely disinfected with chlorine and chloramine to kill pathogens. These chemicals are deadly to animals and must be removed from the water supply. Multi-Test Strips can be used to measure chlorine levels.
Aquarium Co-Op Multi-Test Strips
1. pH – pH is a way to tell how acidic or base the water. The pH range of most freshwater fish is between 6.5 and 8.0. However, some species prefer a lower or higher pH. You can measure it using Multi-Test Strips and the API High Range pH Testing 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. Minerals are essential for healthy animal and plant growth, so we recommend keeping between 4-8 dGH (or 70-140 ppm) for most freshwater aquariums. You can measure it using Multi-Test Strips, or the API GH & H Test Kit Combo. 2. KH is Carbonate hardness (KH). This measures the water’s buffering ability. The KH of water is more stable than the potential for rapid pH changes, which can prove dangerous to fish. It is measured in dKH or ppm (degrees of KH), and for freshwater aquariums, we recommend that it be kept at least 3 dKH or 50 ppm to avoid pH swings. You can measure it using Multi-Test Strips and the API GH &KH Test Kit Combo.
API H & KH Testing Kit Combo
1. Phosphate: Phosphate is a macronutrient that plants need in order to grow well, but excess phosphate can cause algae growth and even harm fish health at high enough levels. Every aquarium has a different fish and plant stocking level, but as a general guideline, some hobbyists suggest 0.5-2 ppm phosphate for low light tanks and 3 ppm or more for high light aquariums that use CO2 injection. Use the API Phosphate Test Kit to measure it.
API Phosphate Test Kit
1. Copper: Invertebrates are especially sensitive to even trace amounts of copper in the water, but some medications contain copper to treat certain fish diseases. To determine the amount of copper in tap water, or to administer copper-based medications to sick fish, use the API Copper Test Kit.
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. To determine if your tank has enough CO2, fill the test tube half way with water. Then, shake the tube for a while and compare it to the chart.
Dennerle CO2 Quick Test
How and when to test 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. Fish keepers might overlook something unusual in their tanks and not test the water. Therefore, we developed the Aquarium Co-Op test strips to be faster and cheaper to use so that you can test more frequently for peace of mind. Here are some common scenarios where we recommend testing 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. It is vital to test the water daily while the aquarium is being cycled. This will ensure that the levels of ammonia, nitrite and nitrate are not too high. You can get the Multi-Test Strips or Ammonia 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. For more information on aquarium cycle, read our full article.
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. Generally speaking, we aim to keep nitrate at 50 ppm or below. If the nitrate level is between 75 and 100 ppm, it’s time for a water change. Live plants are essential for aquariums. They help to reduce the amount of water changes needed by consuming nitrate. You can use our water chart flow diagram to determine how often water changes should be made based on your nitrate reading.
1. Hungry Fish If you notice signs of illness in your pets, or if they are not eating properly, it is time to examine every parameter to diagnose the problem. Check the water temperature, pH, Multi-Test Strips, as well as Ammonia Test Strips. If you suspect an abnormal increase in pH, use the API High Range pH Test Kit. 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. The key is to not only determine if the measurements are within a healthy range but also to evaluate if they differ greatly from the usual values you have seen in the past.
Fish health can be affected by sudden or abnormal changes in the water parameters.
1. Unhealthy plants Nitrate is an important component of balancing the nutrients and lighting in a planted aquarium. Use the Multi-Test Strips to measure the nitrate level and keep it between 25-50 ppm. If nitrate is below this amount, then it may be time to dose some Easy Green all-in-one fertilizer to replenish the 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. If you want to increase plant growth by adding CO2 gas, the Dennerle Co2 Quick Test will help you find out how much CO2 is present in the aquarium.
1. Outside Pond Large outdoor ponds with large amounts of water are best tested using the Ammonia Testing Strips and Multi-Test Strips at least three-to-four times per year. We want to check the water’s performance over the winter at the start of the summer. Check the water quality in the middle of summer. The fish have been eating different foods and the pond evaporates more quickly during warmer weather.
Before you start preparing for winter, ensure that all water parameters have been checked at the end of the pond season. 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. Many hobbyists keep track of water parameters over time by keeping them in a notebook or 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. Enjoy nature every day!