How Ammonia and Nitrites in the Garden Pond Affect the Health of Your Koi and Goldfish

Ammonia and Nitrites are toxic to fish because basically when there is ammonia and nitrites in the water the fish are swimming in their own waste.  If the pond water is high in either the fish will show signs of stress, develop health problems and may die.  Ammonia and nitrites will be a problem as long as the nitrifying cycle of the pond is not developed. 

The Nitrifying Cycle

The nitrifying cycle is the core to a healthy pond ecosystem.  It must be active and strong otherwise the fish end up literally swimming in their own waste.  The simplified version of the nitrifying cycle is this:  Fish eat and give off waste which turns to ammonia which is deadly to the fish.  The aerobic, nitrifying bacteria called nitrosomonas turns ammonia into nitrites (which are also deadly).  The aerobic, nitrifying bacteria called nitrobacter turns nitrites into nitrates which is fertilizer.  The fertilizer then feeds the plants and the fish eat the plants - and so the cycle keeps going.

Whenever there is a missing link the cycle breaks down and the water becomes toxic.  If you don't have adequate nitrifying bacteria you have nothing to change waste into fertilizer. 

Mother Nature cannot possibly supply enough nitrifying bacteria for our overcrowded backyard koi ponds and water gardens without help from us.  Just like you would do for an aquarium you must do for a pond that has fish - you must install a biological filter which will house enough nitrifying bacteria to maintain your fish population.  You can never get enough biological filtration!   For keeping a healthy and clean pond we recommend ProBead or SuperPro Filters.  These low-maintenance filters make it easy to keep the pond clean while providing great biological filtration.

Ammonia

Ammonia is the first step in the nitrifying cycle.  It is produced by fish poop, respiration through the gills of the fish, dead fish or frogs, decaying organic matter and left-over fish food.  If you have a reading of ammonia in the water this means the nitrifying bacteria responsible for changing the ammonia to nitrites (nitrosomonas) is non-existent or weak in the biological filter. 

Ammonia burns the gills of the fish and can permanently damage the delicate gill tissue.  This is called clubbing.  If the gills of the koi or goldfish are scarred white tips it is very possible this fish has experienced a major ammonia problem in the past.  Ammonia kills because it affects the way the gills handle oxygen.  The higher the pH the deadlier ammonia is.  Fish will exhibit many signs of distress when the water is high in ammonia.  They may jump, swim erratically, hang out by the water return, and/or die.  Generally, ammonia will affect the largest fish first.  In fact, we always say that Mother Nature is thinning the pond out her way when the pond has too much fish load for the filtering system to support. 

We specifically use PondCare liquid drop test kits to test our pond water for ammonia.  Not only are they very accurate, they will give accurate readings when certain ammonia detoxifiers are used.  That's very important when you are trying to build up your biological filter.  During season, when the fish begin eating and until the fish stop eating in the winter it's a good idea to test the water for ammonia once a week.  Always reach for the ammonia test kit if a fish dies, the fish are acting strangely or you suspect there may be a problem with the water.  New ponds may require constant testing while the biological filter is seeding.  NO reading of ammonia is acceptable.  If the pH sky-rockets even the lowest amount of ammonia is deadly.  While the filter is seeding (building up nitrifying bacteria), however, you will experience ammonia spikes.  The filter cannot seed without going through a cycle. 

Correcting the Ammonia

Whenever you encounter ammonia readings in your pond water don't panic - but act fast.  The longer the fish are in ammonia the worse things can get.  Here's the steps you should take whenever your tests show ammonia readings:

• Do a major water change.
• Instead of using regular de-chlorinator use Ultimate Water Conditioner.  This will take out any chlorine and, as a bonus, detoxify ammonia up to 2 ppm and that will buy some time before the next water change.
• Test the water every day and do water changes as necessary adding Ultimate each time.
• If you have no biological filter or a filter that is too small for your fish load, add another filter or change it out for one that is adequate.
• Work on building up the nitrifying bacteria by adding either Microbe-Lift PL or Bead Filter Start in you have a bead filter.

Nitrites

Ammonia is only half the equation.  When nitrosomonas is doing it's job the nitrifying bacteria will change the ammonia into nitrites.  Do not confuse nitrites (with an "i") with nitrates (with an "a").  When you get a reading of nitrites that means the nitrifying bacteria responsible for converting nitrites to nitrates (called nitrobacter) is either weak or non-existent.  As a biological filter begins cycling and the bacteria begins developing you'll notice that you'll start with only ammonia readings and no nitrites.  This means that the filter is basically sterile and there is no bacteria present.  As the nitrosomonas begins to develop your ammonia will go down and your nitrites will go up.  That is because nitrosomonas, though not fully developed, is doing its thing and converting some of the ammonia to nitrites.  When the ammonia is completely gone you'll only show nitrite readings.  These readings will go away when the cycle has completed and the nitrobacter has developed. 

Nitrites attack the blood of the koi or goldfish and cause nitrite poisoning.  Signs of nitrite poisoning are brown blood, streaks in the flesh and fins and they may exhibit stress actions such as jumping and acting sick.  They can certainly die if the nitrites are not addressed.

Ammonia detoxifiers do not really work on nitrites (though some manufactures claim they do).  Salting with non-iodized salt (such as Pond Doc's Pure Salt) creates an excellent barrier to protect the fish from the effects of nitrite poisoning.  NO reading of nitrites is acceptable for long but you can have low readings that are not causing stress to the fish as long as you keep the water salted at .3%.  That's 3 pounds per 100 gallons of pond water.

Correcting the Nitrites

Here's the steps you should take whenever your tests show nitrites are present:

• Do a major water change.
• Use Ultimate Water Conditioner instead of the normal de-chlorinator.  It will give you more benefit in this situation than plain de-chlorinator.
• Salt the pond at .3%
• Test the water every day and do water changes as necessary adding Ultimate each time and adding back enough salt to keep it at .3%.
• Continue adding the Microbe-Lift products until the filter seeds and there are no more nitrites.

Nitrates

The nitrifying cycle ends with nitrates.  Nitrates are basically fertilizer.  You need not worry too much about them unless they are excessively high.  Ponds that have plants in them usually will take care of the problem but if you don't have plants you might add a few floaters or something to eat up the fertilizer.  It's not that big of a deal.

More Information About Water Parameters

• Healthy Ponds Have Healthy Bacteria - How to Keep Your Biological Filtration in Shape
• The Importance of Water Parameters
• Mother Nature's Balancing Act - The Nitrifying Cycle
• Seasoning a New Pond

Items You Might Need:

Master Liquid
Drop Test Kit

Nitrite Test Kit

Ammonia Test Kit

Ultimate Water Conditioner

Pond Doc's Pure Salt

ProBead Biological
Bead Filters

SuperPro Filters

Microbe-Lift PL

Microbe-Lift's
Super Start for Bead Filters

Know Your Gallons!

Heavy Duty Water Meter

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