Water Quality Parameters


If your koi fish are showing symptoms of illness it obviously needs to be diagnosed and remedied. However, treating the koi without resolving the underlying problem will inevitably bring you back full circle and frustrated. Water quality is the number one preventative measure to keeping healthy fish.



All ponds will at times have parasites and diseases lurking within their waters but keeping the parameters in check will maintain your koi’s immune system and prevent them from developing ailments to begin with.

The Nitrification Cycle

Protein from uneaten food, plant matter, fish waste, and respiration converts into Ammonia.

Nitrosomonas a naturally occurring bacteria convert ammonia into nitrite.Nitrobacter another naturally occurring bacteria, convert the nitrite into nitrate.

Nitrate is a nutrient which feeds plant and algae growth.

Plants and algae are eaten and recycled by fish. Plant life constantly growing new foliage and shedding their old which decomposes and is added back to the cycle as ammonia

Ammonia ~ NH3 / NH4

Ammonia is made up of nitrogen and hydrogen which enter the pond via fish waste & respiration, decomposing matter and other organic material. Ammonia exists in two forms, free ammonia NH3 and ionized ammonia NH4. NH3 or free ammonia is the more lethal of the two and is dangerous to fish at very small doses.

The koi keeper also needs to be aware that as temperatures and pH levels rise, ammonia becomes increasingly more toxic. Because of this and also the fact that most test kits test for total ammonia or NH4, it’s necessary to use a chart to make proper diagnosis of ammonia danger levels in your pond unless your test reads NH3.

Here is an excellent, well researched chart with directions and explanations for use: "AMMONIA TOXICITY CHART"

Why Monitor?

Unacceptable ammonia levels can cause many problems including:

* Hyperplasia ~ a cellular condition which restricts the amount of oxygen a koi can absorb.

* Organ Failure

* Vulnerability to other infections disease. Fin rot, dropsy and gill problems are common.

* Death

Maintaining Proper Levels:

Parameter Target: 0.0ppm - 0.25ppm


1) Add zeolite to filters.

Zeolite can be placed in a mesh bag and dropped into any filter to absorb and protect against ammonia.

2) Adequate bio-filtration ~ Bio-filters contain naturally occurring Nitrosomonus bacteria which metabolically convert ammonia into nitrite.


Emergency Procedures:

*10-20% daily water changes with suitable water.


WARNING: Mixing ammonia with chlorine or chlorinated water will off gas toxic gas which can be fatal to humans and other living creatures.


Nitrite ~ NO2

Ammonia is broken down into nitrites by “Nitrosomonas” a naturally occurring bacteria. Nitrites are broken down into nitrates by nitrobacter, a second type of bacteria. If your koi show signs of irritation, or abnormal behavior it may be due to high nitrite levels. High nitrite levels reduce the koi’s blood cells ability to carry oxygen.


Why Monitor?

High nitrite levels reduce ability of the koi’s blood cells to carry oxygen which can cause:

* Browning of the gills.

* Overall poor health leading to susceptibility of other problems such as disease, parasites & bacterial infections.

* Death


Maintaining Proper Nitrite Levels:

Parameter Target: 0.00ppm


1) Adequate bio-filtration


Emergency Procedures:

*Adding salt to the water can reduce the toxicity of nitrites however be aware salt content can become a problem with some other pond treatments, test results and medications causing a whole other set of problems.

*10 - 20% daily water changes with suitable water.

Nitrate ~ NO3

Nitrites are converted into nitrates by “Nitrobacter” a naturally occurring bacteria. Nitrates are the last stage of the nitrification process and the least harmful to koi fish.


Why Monitor?

High nitrate levels are relatively harmless to koi. They can however:

* Have an effect on koi growth.

* Feed blanket algae to overgrowth whereby effecting ph and oxygen levels.

* Have ill effects on koi eggs and fry.


Maintaining Proper Nitrate Levels:

Parameter Target: 0 - 50ppm


*Vegitation filter


Emergency Procedures:

*10 - 20% daily water changes with suitable water.


PH is a measure of the balance of hydrogen & hydroxyl ions. A low Ph being acidic (more hydrogen ions) and a high ph being alkaline (more hydroxyl ions). A ph of 7 is neutral with the hydrogen & hydroxyl ions perfectly balanced. Koi can live in a wide range of PH levels from 6.8 to 8.5 as long as it is stable. Rapid fluctuations in the PH are more fatal than a low or high level that is stable. The Alkalinity of the water acts as a PH buffer stabilizing it against rapid fluctuations.


Why Monitor?

* Ph should be monitored regularly in a koi pond such as biweekly as the PH effects the toxicity of ammonia.

Acidosis ~ (Acid poisoning) PH to low:

* Decreased ability for the gills to extract oxygen. You may see irregular gill movement or gasping.

* Excess mucus.

*Redness of the skin.

*Stressed immune system which may result in other infections and disease.


Alkalosis (Alkaline poisoning) PH to high:

Same symptoms as acidosis but may be combined with severe fin and or gill damage.


Maintaining Proper Levels:

Parameter Target: 7 to 8

A gradual daily fluctuation is normal so testing should be done at the same time preferably mid day as it will read lower in the morning and higher in the evening.


*Crushed oyster shells, crushed coral or aragonite in a filter act as a ph buffer stabilizing and eliminating ph problems.

*Monitoring alkalinity will give advanced warning of ph stability which may allow preventative measures before a rapid and potentially fatal ph crash occurs.


Emergency Procedures:

* PH Up and PH Down liquid products.

* Baking soda will raise the ph level.

* 20 to 50% water change with suitable water.


Dissolved oxygen content in your pond water is critical to your koi as well as the essential good bacteria in your bio-filter. Oxygen levels can be depleted by a heavy algae blooms, rising water temperatures and fish stocking rates to name a few. Koi gasping at the surface is a sure sign levels are dangerously low.


Maintaining Proper Levels:

Parameter Target: Min. 8.0ppm Dissolved oxygen

Monitor closely during algae blooms or high temperatures.


*Plants ~ A plant filter besides converting carbon dioxide into oxygen, also consumes nitrates. Other aquatic plants such as floating plants, marginals or submersible plants will also ad oxygen. Large gravel on the surface of potted plants will help prevent koi from rooting in the growing media.

* Agitation ~ Adding a bubbler, venturi or even raising the return so it falls into the pool. An additional pump could be used to operate a fountain.


Emergency Procedures:

* Aerate

Hardness (GH) General (CA)
Total Hardness 

Hardness for koi is (GH General Hardness which is Primarily Calcium Hardness (CA). Essentially (CA) is what you need to test, monitor and maintain for koi fish.

Hardness is the overall concentration of divalent salts (calcium, magnesium, iron, etc.) Calcium and magnesium are the most common sources of water hardness. Calcium and magnesium are essential for bone and scale formation in fish. The most critical component of total hardness, however, is the calcium concentration or “calcium hardness.” Environmental calcium is crucial for osmoregulation, the biological process that maintains precise levels of internal salts for normal heart, nerve and muscle function.


Why Monitor?

* Calcium Hardness is largely about health benefits to the koi.

* An essential component in the production of enzymes and hormones that regulate digestion, energy, and fat metabolism.

* Helps to control nerve transmission, and release of neurotransmitters.

* Assists in maintaining cells and connective tissues in the body.

* Calcium also helps in blood clotting, healing and stress.


Maintaining Proper Levels:

Parameter Target:100 - 250ppm


*Crushed oyster shells or crushed coral all have a calcium content and are beneficial as a pH buffer as well as a source of bicarbonates for alkalinity.


Emergency Procedures:

* Calcium Chloride will rapidly increase calcium hardness levels.

Alkalinity: KH Carbonate Hardness

Total alkalinity indicates the entire quantity of titratable bases present in water, primarily bicarbonates, carbonates and hydroxides.

The most important components of alkalinity are bicarbonates and carbonates.

Total alkalinity is a measure of water's resistance to change in pH also called “buffering capacity”. It buffers the ph by neutralize acids in the water created by fish and bacterial waste.

As long as there is a reserve of alkalinity, the pond water pH will remain stable.


Why Monitor?

* Monitoring alkalinity in a koi fish pond regularly gives you an advanced warning and time for coorsction of a problem before the impending doom of a dangerous and disasterous pH crash.


Maintaining Proper Levels:

Parameter Target: 75 to 200ppm


* Baking soda (bicarbonate of soda) will quickly react with the acids to help balance alkalinity. However, be aware baking soda can also raise the pH so add it in intervals and monitor the pH.

*Crushed oyster shells or crushed coral are composed of calcium carbonate and will maintain alkalinity.


Emergency Procedures:

* One third cup of baking soda per 1000 gallons of water will raise the KH level by 25 ppm.

* 20 to 50% water change with suitable water.

Water Testing

For water testing I use an eXact® Eco-Check Dual Wavelength Photometer.

It is uses a narrow band wavelength filter for  0.01 ppm (mg/L) precision

accuracy.  The long lasting LED  photometer eliminates the need for the guess work of visual color matching.

I have the older version because I purchased and have been using it for over 5 years now. It tests all of the parameters above except oxygen. The newer version includes Phosphate, copper & chloride.


For Oxygen level testing, I use the LaMotte® Dissolved Oxygen Test Kit. It’s a sort of science class experiment to use but not complicated and quite a bit of fun.

I’ll be adding a video of the process when I get the chance.