Ammonia in Ponds is Deadly for Koi and Pond Fish. What is Aeromonas Alley?
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Ammonia in Ponds

Of all the water quality

parameters that affect fish, ammonia is the most important after oxygen, especially in intensive systems. Ammonia causes stress and damages gills and other tissues, even in small amounts. Fish exposed to low levels of ammonia over time are more susceptible to bacterial infections, have poor growth, and will not tolerate routine handling as well as they otherwise would.

Ammonia is a toxic inorganic chemical made up of nitrogen and hydrogen. In healthy ponds and tanks, ammonia levels should always be zero. Presence of ammonia is an indication that the system is out of balance.

Ammonia, NH3, measured in parts per million (ppm), is the first measurement to determine the "health" of the biologic converter. Ammonia should not be detectable in a pond with a "healthy" bio-converter. The ideal and normal measurement of ammonia is zero. When ammonia is dissolved in water, it is partially ionized depending upon the pH and temperature. The ionized ammonia is called ammonium and is not particularly toxic to the fish. As the pH increases and the temperature drops, the ionization and ammonium decreases which increases the toxicity. As a general guideline for a water temperature of 70° F, most Koi would be expected to tolerate an ammonia level of 1 ppm for a day or so if the pH was 7.0, or even as high as 10.0 if the pH was 6.0. At a pH of 8.0, just 0.1 ppm can be dangerous.

Click Here for "Aeromonas Alley"

If the pond becomes polluted with ammonia or nitrite, increase the aeration to help gas off these pollutants. Undertake regular partial water changes to dilute the ammonia or nitrite, reducing the frequency as pollutants decrease. Always use a water purifier or treatment to dechlorinate the incoming tap water.

Effects Of Ammonia

Ammonia tends to block oxygen transfer from the gills to the blood and can cause both immediate and long term gill damage. The mucous producing membranes can be destroyed, reducing both the external slime coat and damaging the internal intestinal surfaces. Fish suffering from ammonia poisoning usually appear sluggish, often at the surface as if gasping for air.

Source Of Ammonia

Ammonia can get into your pond from several places:

  • Usually and primarily from the gills of the fish.
  • The decomposition of organics
  • If your tap water contains chloramines, using a dechlorinator alone will release ammonia from the chloramine. The additional use of a binding agent for ammonia is recommended.

Over stocking of Koi and Pond Fish is the Fastest way to raise the Ammonia Levels in your Pond. You should have no more than one inch of Koi per 10 gallons of water. Koi are measured from the tip of their nose to the end of the fin.

Ammonia accumulates easily in aquatic systems because it is a natural byproduct of fish metabolism. All animals excrete some waste in the process of metabolizing food into the energy, nutrients, and proteins they use for survival and growth. In fish, the principal metabolic waste product is ammonia. Because it is continuously excreted and potentially lethal, successful aquaculture operations must therefore incorporate methods to detect and eliminate ammonia before it can accumulate and harm fish.

A byproduct of protein metabolism, ammonia is primarily excreted across the gill membranes, with only a small amount excreted in the urine. The decay of uneaten feed and organic matter create small amounts of ammonia, but in most aquaculture systems, fish themselves are the primary source of the compound. The more feed a fish receives, the more ammonia it will produce. However, even a starved fish will produce some ammonia.

Routine tests of your pond water for ammonia are recommended and a satisfactory test result is no detectable ammonia.

The use of two or three-reagent salicylate-based test kits are recommended as they may be used effectively with most ammonia binders. These kits show yellow with no ammonia and turn progressively more blue-green with increasing ammonia in the test water.

The use of one-reagent Nessler-based test kits (clear to yellow-orange with increasing ammonia) is discouraged as they produce false readings when ammonia binders are present.

Ammonia Sensitivity Chart

pH can be increased by adding aeration to strip CO2

pH can be reduced by lowering aeration to retain CO2

Nitrite is more deadly in acid pH 6.0-7.0 water

Ammonia is more deadly in alkaline pH 8.0-8.6 water

Source - Debby Young article in KOIUSA, Volume 20, Issue 2

Aeromonas Alley

Every year fish in cold climate ponds struggle through extreme stress and, in some cases, die due to "Aeromonas Alley".

What is "Aeromonas Alley"?

"Aeromonas Alley" is defined as when your pond water temperature ranges between 42° F and 62° F. Between these temperatures, the deadly "Aeromonas/Pseudomonas" (AP) bacteria grow much faster than your fish's weak immune system. This makes it very difficult for your Koi to fight off this deadly bacterial attack, causing ulcers, fin rot and more. In fact (AP) remains strong throughout the warm summer months. That's why it's so important to keep the numbers of (AP) as low as possible in your pond water.

Also beware of "Aeromonas Alley" in the fall when your Koi pond water starts dropping below 65° F. At 65° F the immune system of your Koi and pond fish starts to decline and weaken. By the time your pond water temperature drops to 60° F the immune system of your Koi and pond fish is operating at less then 50% efficiency. However, the deadly (AP) bacteria is still strong and active and takes this opportunity to make their deadly attack on your weaken Koi and pond fish.

References: Aqua Meds

Treatment Of Ammonia

Chemical treatments to counteract ammonia toxicity are available commercially under various trade names. These treatments, most of which are based on formaldehyde, chemically change the form of the ammonia into compounds that are not harmful to the fish. They do not actually remove it from the pond. The bio-converter bacteria still does the actual removal.

Although most of these products use a dosage of 50 ml per 100 gallons to chemically bind up to 1 ppm of ammonia, be sure to check the manufacturer's directions before use as those containing formaldehyde can cause an overdose if not used correctly.

Products to help you lower your ponds ammonia are Ammo-Lock, Microbe-Lift Ammonia Remover and Dry Ammonia Remover.

When ammonia is detected (assuming a pH of about 7.5):

  • Increase aeration to maximum. Add supplemental air if possible.
  • Stop feeding the fish if detected in an established pond, reduce amount fed by half if starting up a new bio-converter/pond.
  • Check an established pond bio-converter for probable clean out requirement.
  • For an ammonia level of 0.1 ppm, conduct a 10% water change out. For a level of 1.0 ppm, conduct a 25% change out.
  • Chemically treat for twice the amount of ammonia measured.
  • Consider transferring fish if the ammonia level reaches 2.5 ppm.
  • If starting up a new bio-converter/pond, discontinue use of any UV Sterilizers, Ozone Generators, and Foam Fractionators (Protein Skimmers).
  • Retest in 12 to 24 hours.
  • Under Emergency conditions only, consider chemically lowering the pH one-half unit (but not below 6.5).

CAUTION: If the tap water has a higher pH than that of the pond or if the tap water contains Chloramine, adding the replacement water may make the situation worse.

Ammonia Poisoning

Not only is ammonia produced by bacterial mineralization, it is also pumped into the water by the fish excrement. Basically, fish are swimming in a pool of their own filth and it is this that poisons them, causing damaged tissue, especially of the gills and kidneys. Ammonia poisoning also lowers resistance to disease, making the fish more susceptible to death, which is why aquarium hobbyists and pond enthusiasts refer to fish that have been poisoned by high levels of ammonia as “New Tank Syndrome.”

Along with toxic levels of ammonia, high nitrite levels also pose a problem. Nitrite poisoning keeps red blood cells from taking in oxygen, converting the hemoglobin in red blood cells to methemoglobin, a form of hemoglobin that does not bind oxygen, heightening the possibility of tissue hypoxia.

A single Nitrosomonas cell can covert about the same amount of ammonia that it takes 1 million standard pond bacteria (heterotrophic bacteria) to convert.

In order for nitrifying bacteria to make the biggest impact in restoring a natural nitrogen cycle to your pond, follow these four tips:

  • Make sure that your pond has micronutrients for nitrifying bacteria, most importantly, ATP (Adenosine Tri-Phosphate.) This nutrient provides energy for the nitrifying bacteria to carry out cellular functions. Phosphates are also needed, particularly because Nitrobacter cannot oxidize nitrite without it.
  • It is also important to make sure that the temperature of your pond is conducive to the growth of nitrifying bacteria. A good temperature is 75 to 85 degrees Fahrenheit. Ten degrees colder and its growth rate is substantially cut in half. At 120° Fahrenheit, nitrifying bacteria cannot live to convert another day.
  • Nitrifying bacteria also need specific pH levels in order to thrive. pH must be slightly basic at 7.8 to 8.0 for Nitrosonomas and 7.3 to 7.5 for Nitrobacter. Bacterial growth is stunted the more acidic the water pH gets.
  • Dissolved oxygen levels must exceed 80% saturation in order for maximum nitrification. If levels drop below 2 parts per million, nitrification will not occur.

Principal Sources of Ammonia

  • Excretion by fish as a normal part of their metabolism
  • The breakdown of protein in uneaten food or dead fish that may have been overlooked.

As ammonia is released into the water by either of these processes it may take one or two forms:

  • Free Ammonia (unionized ammonia, chemical symbol NH3). This form of ammonia is highly toxic to fish.

  • Ammonium (ionized ammonia, chemical symbol NH4+). This form of ammonia is virtually non toxic to fish.

To determine the amount of Free Ammonia present, pH and temperature MUST be known. Free Ammonia should not exceed 0.02mg/l in freshwater. Above this level free ammonia causes the fish stress and at higher levels it may cause damage to gills and many internal organs, eventually resulting in fish deaths.

Levels of TOTAL AMMONIA (mg/l) that maintain FREE AMMONIA at or below 0.02mg/l at a range of pH and temperatures

Temp F
6 6.5 7 7.5 8 8.5 9
32° 250 77 24 7.7 2.4 0.78 0.1
41° 154 50 16 5 1.6 0.52 0.07
50° 105 34 11 3.4 1.1 0.36 0.05
59° 74 23 7.5 2.3 0.75 0.25 0.04
68° 50 16 5 1.6 0.52 0.18 0.04
77° 35 11 3.5 1.1 0.37 0.13 0.03
86° 25 8 2.5 0.8 0.27 0.1 0.03

Ammo Lock by PondCare®

Ammo-Lock Instantly detoxifies ammonia from fish waste, tap water, uneaten fish food, decomposing plants, and algae. Prepares tap water for plants and fish.

16 oz Size Treats 1,920 gal

~Price $18.00

Resources: Norm Meck from


You are here: Home > Build A Koi Pond > Water Quality > Ammonia in Ponds

Ammonia and your New Koi

When a new fish is purchased and sent home in a plastic bag with oxygen and a little bit of water, and the fish is in the bag for a considerable period of time, ammonia will accumulate in the water. The pH of the water often lowers because of the fish’s respiration producing dissolved carbon dioxide. This lower pH keeps the ammonia from being as toxic because it is ionized to a large extent to the ammonium ion. Do Not open the bag until ready to remove the fish because, if it is opened and the carbon dioxide is released, the pH will increase making the ammonia more toxic.

When the Koi finally reaches its new pond, the bag should be floated in the pond to equalize the water temperatures before the fish is released. Do not add pond water to the bag! This can be very dangerous for the fish. The pond water will likely raise the pH of the water in the bag, converting the ammonium ion back to toxic ammonia.

The best technique is to float the sealed bag (in the shade or covered with a cloth) for about 15 minutes to equalize temperatures, and then open the bag and lift or net the Koi of the bag into the pond or quarantine tank. Ideally, the water temperature change should be less than 5° F (3° C) and the pH difference should be less than a 0.5 change in the pH unites. The most important factor is to get the Koi out of the transport water as soon as possible.

Ammonia Test Kit

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Reducing the level of Ammonia

  • Dilution by water changes
  • Reduction of stocking densities
  • Improvement of feeding and general husbandry procedures
  • Improvement of biological filtration
  • Use of ion exchange materials

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