New Pond Syndrome: How To Clear Green Pond Water

new pond syndrome symptoms solutions tips

In this article on pond maintenance we will recap our interview with pond care expert Christian Shostle, who covers handling new pond syndrome (NPS), setting parameters to measure syndrome effects, and planning action steps to master your water quality.


Learn How To Clear Green Water & Identify New Pond Syndrome

Table of Contents About NPS


What is New Pond Syndrome?

New pond syndrome (NPS) is characterized by inhabitable or discolored water, diseased fish, ammonia spikes, and several other potentially fatal symptoms. The most common cause of NPS is a premature addition of too many fish, resulting in a break of the bio filter.

It’s important not to confuse new pond syndrome with only green pond water, which in many cases is a healthy part of the natural water cycling process. A key differentiation between these two phenomena is the effect on the fish – monitoring your fish health and water quality will prevent any misdiagnosis of NPS. Learn to tell the difference between green pond water and new pond syndrome in this article.


How to Tell If You Have New Pond Syndrome.

If your pond is turning dark green, there is foam, and dark green / black slimey algae buildup on sidewalls, than you are on the way to new pond syndrome. The short green carpet algae is good and should be left alone. Algae problem? Learn tips for how to remove string algae from your pond.

If you don’t address this issue you’ll notice your fish will develop ulcers, body sores, fin rot, mouth rot, and/or gill rot from not getting enough of the proper aeration/filter in your pond. The filter is also feeding your negative water quality with anaerobic activity occurring in the filter.

Waiting to make a change in your water quality will end up costing you more in maintenance. Make sure you stay on top of testing for correct pond parameters. The addition of nitrifying bacteria is highly recommended for this situation. You can use Bio Filter Booster/starter, for example.


 Symptons of New Pond Syndrome.

Symptoms of fish death from ammonia and nitrite poisoning can range from white spots, ulcers, fungus and fin rot, which are secondary infections arising from stress caused by the poor water conditions.

If pond is less than three months old, you can recognize these symptoms of NPS in your fish or water:

  • Not eating
  • Scratching
  • Sulking
  • Fish gasping
  • High nitrite readings
  • High ammonia

Tap water is percolated through underground sediments and contain essential salts and minerals important for fish welfare. Although tap water is the best source, it can have other additives, like chlorine so a water conditioner should be added to ensure the water is safe for the fish.


What If the Green Water Won’t Go Away in My Pond?

Blue Green Algae Growth Using Nualgi Ponds has many benefits to balance your water to help fix new pond syndrome and create healthier water. But that alone will not solve your problem, removing the highly concentrated water and increasing aeration are also extremely important steps.

If high concentrations of ammonia persist, then add air to the water to promote growth of ammonia and nitrite eating bacteria. In the unfortunate event of your pond getting new pond syndrome, replace up to 25% of the water weekly to reduce high concentrations and then add extra air into the system. Also try reducing the amount of feed given to the fish.

Ammonia is present is alkaline water, a pH of 7.1-14. If ammonia is present in small amounts, a warmer temperature will make the water more alkaline, in turn making it more of a threat. Nitrite is present in acidic waters, a pH of 0-6.99.


Important Milestones In the Pond Cycle to Prevent New Pond Syndrome

First, the pond has to cycle and that can take up to 80 days. If everything is going right, your pH level will begin to stabilize to the 9’s getting closer to the optimal 7.5.  You won’t have to worry about ammonia at this point. The pond will start showing a different shade of green.

Image from

Start adding plants with a minimum 60% surface covered. The plants will decay and release other agents in to the pond, thus creating a “stew of life” after 2-6 weeks while the pond stabilizes further.

Testing pH often is best indication if pond will be safe to add Koi fish.

Once the pH is around 8-8.2 and no higher 8.5 you can start considering the addition of fish. The proper pH of a mature pond should be around 6.5 to 8.5, with constant but little fluctuation.

The pH will continue to reduce through 70-90 day marker. This is when the algae begins to bloom. Now you should begin tracking nitrate and phosphate levels to make sure it is balanced out. Most people will use a master kit for all the testing. It is the most reliable way to test as the strip type tests often give false readings.

Nitrite levels of 0 – 50 ppm is good 50-80 ppm is too high. Ultimate goal is 0 ppm at all times.

After adding aquatic plants and have stabilized pH, you can begin adding fish:

  • Start with a small amount of fish, six at most. (based on size of pond)
  • Constantly test the water. If in 3 weeks your pond is still in “good” standing, you can add a couple more fish.
  • About 3 weeks after adding fish you may still see green water.
  • About 5-6 weeks after it will have naturally turned to clear water.

Christian instructed us to always buy 3 times your water volume on your filter/pump if you plan to keep koi/plants. Replace filter material with tough clay material. He suggests you use other filters on top of that, but normally in the first few months do not use the fine grade pad.


Why Does It Matter to Koi Fish?

Fish release waste in the form of ammonia. As the ammonia builds up to high concentrations it affects the fish’s gills and vital organs. Goldfish can go in at anytime after the cycle, Koi  fish are so inbred that they are not as resilient and are delicate to ammonia, nitrates, and phosphates.

You can also create long term issues in their liver that are not noticeable right away. When fish are found near water inlets, gasping of air that is a major sign of high ammonia and nitrite concentrations. Removing fish to quarantine is not an end solution as any issues already present in the water will continue to infect other inhabitants.

In turn, nitrite is also poisonous to the fish. A bacteria called Nitrosomonas break down ammonia into nitrite, nitrite is in turn utilized by other bacteria that is essential for proper filtration. However, as the ammonia concentration goes down, the nitrite concentration goes up. Nitrite affects the fish’s red blood cells, not allowing them to access the water’s oxygen.


Opening a New Pond with Koi Fish? Take Your Time!

It can take up to three years for a pond to completely mature, so relax and be patient.

In the excitement of opening a new pond, you must resist the urge to put everything in at once. Be aware that there are certain steps that need to be taken for the first 30 days prior to adding fish. To start, take measurements every week to be sure you are ready to add fish to your pond.

Premature addition of fish can quickly spread disease and lead to fish loss.

To begin our conversation with Christian we were informed not be afraid of green water, this is in fact a part of the natural pond cycling process. The best method is to let the green water come and stay for a few months. This is proof the water is sustaining life. As the bacteria dies, the algae dies out and starts the food chain. Remember that nothing can immediately overcome the process of maturing water. Nature has it’s way of creating life in the body of water to balance it out.

About Christian Shostle

Career: Owner of Cali Koi

Location: North Hollywood, Los Angeles CA

Aquaculture Background: Fascination in the chemistry of water since 12, always with a pond or fish tank nearby. Traveled through the majestic hills of Japanese Koi farms in the Niigata region and learned the zen teachings not so common in US Koi keepers.

pond water chemistry enthusiast





Do You Have Any New Pond Syndrome Tips?

We would love to hear your feedback in the comments section below. There are always different ways of treating issues in your pond, please tell us more about your situation and what you did to fix new pond syndrome. Thanks for reading!

Most popular blogs:

Sign up for our newsletter

Our Pond Blog and Pond Help pages are full of helpful resources to make managing your pond easier.

If you’re still struggling, don’t hesitate to reach out to our team of Pond Experts.

Meet the Nualgi Family!

Signing up will send you a coupon code for 10% off your first purchase. We’ll also keep you updated with loads of helpful pond maintenance tips and giveaways.

    Your Cart
    Your cart is emptyReturn to Shop

    This website uses cookies to ensure you get the best experience on our website.

    Sign up for our newsletter and receive 10% off your first purchase!