How to Test Pond Water & How to Read Results

When was the last time you tested your pond's water? Even if the water is crystal clear, you can have too much ammonia or imbalanced pH levels. Catching these issues before they start causing water quality issues makes it easier to maintain a healthy pond. Regular water quality tests let you know what's going on beneath the surface so you can use a water treatment if needed. Water quality tests are an important indicator of pond health. Learn more about how to conduct a water quality test and what to look for. 

How often should you test your pond water?

When the weather is warmer in the summer and late spring, you will want to test your water biweekly. Water quality issues tend to be more common in the summer. These tests can help you see if you have too much nutrients in the water to help prevent algae blooms. In the other months, you can typically get away with testing the water only once a month. 

DIY Water Tests

If you want to conduct your own water tests, you have two options: strip or liquid dropper. You can typically find at-home water quality tests at Lowes or your local aquarium. Strip tests use special types of paper that change colors in reaction to different contaminants in the water. They are typically less accurate than a liquid dropper test. 

Strip Test

When using a strip test, follow the directions on the box, as they may differ from brand to brand. Usually, it will tell you to dip the strip in a sample of pond water and then wait a minute. You can then compare the colors on the strip to different indicators. The shade of color, how light or dark it is, will let you know what the levels are for each condition. 

Liquid Test

Liquid testing takes more time but is often more accurate. These types of tests come with vials for you to take samples of the water. Each vial tests for a different contaminant or condition. You take a vial with the water sample and then add the liquid reagent that correlates with what you're testing for. This reagent will react with the water and turn a color. You can then compare it to a chart to see how high or low the level is. 

Get your water tested

You can also take your water to get it tested professionally. Many local aquarium and pet supply stores offer water testing as a service to their customers. This testing may be free or have a small charge. You can drop off samples of your pond water (check and see if they provide containers first). If they offer, testing will give you a report with their findings after. 

How to Read Results:

Ammonia - Fish release ammonia in their waste. If ammonia levels are too high, it can cause stress and illness in your pond fish. Even fish-less ponds can have high ammonia levels from the breakdown of organic materials by the "bad" bacteria. The "good" or beneficial bacteria in the pond can typically break down ammonia into harmless nutrients and gasses, but overcrowding and other conditions can cause the levels to spike. 

Acceptable levels: Close to 0 as possible, with anything over 0.25 PPM calling for a partial water change and water treatment.

pH - pH tells you how alkaline or acidic your pond water is. The ideal range for the water is around 7.4 for fish. If the levels fall below 6.5, the water becomes too acidic. The water can become too alkaline if it goes above 9 and can cause ammonia to become more toxic to fish.

Healthy range: 6.5 to 9.

KH - KH measure the level of carbonate hardness (calcium carbonate) in your pond. Calcium carbonates feed the beneficial bacteria in your pond, and without them ammonia levels can rise.

Acceptable levels: 125 PPM, but can safely shift 20 PPM in either direction

Nitrites - Before bacteria turn nutrients into nitrates, which are less harmless, they convert them to nitrite. It's part of the nitrogen cycle. When too high, nitrites can prevent fish from absorbing oxygen in the water and cause health problems. 

Acceptable levels: Less than 0.25 PPM.

Nitrates - When bacteria break down nutrients in the pond, they produce nitrates, which are nutrients for plants. If the plants don't absorb enough, it can cause high levels in your pond. When the nitrates are too high, it can fuel algae blooms and can cause illness in your fish and lower their immune system. 

Acceptable levels: Between 20 ppm and 60 PPM. 

Phosphates - Tap water, fish food, and fertilizers contain phosphates, which then find their way into your pond. Phosphate levels may spike after heavy rainfall or if you do a water change. While phosphate isn't particularly dangerous to your fish, it can fuel algae blooms, hurting water quality and deplete the pond of oxygen.

Acceptable levels: Less than 0.05 PPM. 

Chlorine - Before adding fish to your pond, check for chlorine to make sure it is safe. Tap water contains chlorine, and it's harmful to fish. You will need to treat the water with a Chlorine Remover first. Chlorine levels can also spike if you need to do a water change. 

Acceptable levels: Ideally, 0 but less than 0.01 PPM. 

Testing your pond water is an important maintenance step to check for water quality issues that may not immediately cause problems. When levels of certain contaminants get too high, it can cause health problems for your fish, even death in some cases. You can do a water change or use a water treatment to help rebalance your pond if the levels are off. Regularly testing your water helps to prevent water quality issues and lets you monitor your pond's health.