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What Is In Pond Water?

Water is not only one of the most abundant resources on earth, it also one of the most scarce. Although it covers three quarters of the Earth’s surface, only three percent is fresh water, and only one percent of that is available to us for our daily water needs. No one knows more about the importance of water than pond owners. And with the droughts that many parts of the country experience, water has been the topic of many discussions. But as a pond owner, do you know whats in your pond water? Do you know what you really need to protect the plants and the ecosystem as a whole? 

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pH and Alkalinity

Yes, we are going back to high school for a chemistry review! Exciting, isn’t it?? Lets start off by reviewing pH, which is a measure of the concentration of hydrogen ions in a solution. The pH scale ranges from 0-14, with 7 being neutral. Values less than 7 are considered acidic, and values greater than 7 are basic or alkaline. There’s a 10-fold increase between each number on the scale, meaning that a pH of 4 is 10 times as acidic as a pH of 5.

According to the EPA, a pH level ranging between 6.0 and 8.5 is a good profile for any natural stream, yet people are always debating about this. Koi experts believe that for their fish to thrive, pH levels should not be lower than 7.0 and should remain fairly neutral. The truth is that if you are merely raising Koi as pets, your best bet is to watch their behavior to see if conditions are suitable for them. Ideal conditions for ponds range from 7.5 to 8.5, below 6.5 can be too acidic for Koi. Don’t worry too much if the pH changes, this is normal and the levels can very greatly over a 24-hour period. Placing an aerator in your pond can stabilize the pH and increase dissolved oxygen levels.


According to Dr. Eric Johnson, ammonia is the No. 1 killer of fish in a new pond. “Ammonia is a big problem in new systems because the bacteria that would naturally convert ammonia are not established,” Dr. Johnson says. “As well, even in established systems, ammonia may accumulate in springtime when the water is cold but fish are eating, because filter bacteria have not emerged usefully from hibernation.”

So, how do you know that there are high amounts of ammonia in your system? “Ammonia accumulations cause reddening of the skin and disability of the gills by its direct caustic effect on these surfaces,” according to Dr. Johnson. “Fish suffering in water with high ammonia accumulations will isolate themselves, lie on the bottom, clamp their fins, secrete excess slime, and are much more susceptible to parasitic and bacterial infection.”

Ammonia is less toxic at a pH level below 7.4, but that doesn’t mean you have to worry. Ammonia doesn’t start to get too toxic until you reach pH levels over 8.0, and it also depends on the rest of the elements in your system.


Just because there’s oxygen throughout our atmosphere doesn’t necessarily mean that there is enough to sustain life in your pond at all times. While fish can survive without food for a short period of time, oxygen cannot be compromised – even for a few minutes. There are two times, if you aren’t careful, when oxygen may be scarce for your fish … winter and summer. However, if you have a pump re-circulating the water in the pond, this won’t be a problem because the water will be constantly oxygenated.

In the wintertime, many pond owners choose to shut down their pond’s circulation system. To replicate the oxygenation; keep a hole open in the ice to allow gasses to escape and add a supplemental pump or aeration system set inside the pond, bubbling near the surface of the water. heater/deicer can also be used to keep a hole open in the ice, but never without the re-circulating or air pump.


Regardless of the season, the best solution for keeping oxygen available in your pond is to have a continuously operating water pump and a sufficient filtration system, like the BIOFALLS® filter. This keeps the water moving at the waterfall, and introduces more oxygen to the water with the constant water flow.

Nutrient Levels

Nutrient levels effect the water clarity and the amount of algae you may encounter during certain weather changes. After all, nutrients are what algae feeds on in your pond, and if there are high amounts of nutrients, you’re going to have more algae. That’s where the bacteria come into play. By putting beneficial bacteria into your pond and allowing it to establish itself in the system, you have something that competes with the algae for the nutrients.

So, how do you get higher nutrient levels? Well, allowing fertilizer from the grass to run off into your pond can produce an algae bloom almost instantly. Fertilizer tabs that are placed into a plant pocket could also release nutrients from the soil, and can create string algae. This doesn’t mean that you should stop fertilizing your plants though … just remember that a little string algae is no match for bacteria and that the end result is worth it.

Mulch that gets accidentally kicked into your pond, along with decaying aquatic plant material, and other organic matter that finds its way into your pond will also produce a spike in the nutrient level. You might also want to pay close attention to how much you feed your fish – un-eaten food can also contribute to excess nutrients in the pond water.


The bottom line, when it comes to keeping your pond healthy and providing your aquatic life with the best possible conditions, is consistency. Any kind of dramatic change in your pond’s water is shocking to the aquatic life, but if changes are made gradually, everything should be okay. Another important thing to remember is that if nothing is wrong in your pond, don’t try to fix it. If your fish are exhibiting normal behavior, don’t do anything to change the pond’s environment, keep well enough alone. If you’re having water problems with your pond, give us a call, we would love to help!