The Importance of Pond Water Quality
We koi keepers refer to ourselves as the keepers of water. That’s because we know that high-quality water relates directly to high-quality fish, the residents of that water. It’s imperative to conduct regular water testing to identify issues before they become a problem. This testing enables us to be proactive and ensure excellent water quality. We do this to keep the koi healthy in your beautiful koi pond.

The Best Water Test Kits and Meters
The water quality test kit you buy should be able to test pH, ammonia, GH, KH, and nitrite levels in the water, as they are the most important parameters. In addition, you may want to test salinity, oxygen content, nitrate levels, and ORP. Test kits contain reagents to mix with the water. After adding the reagent to the water in a test tube or other collection device, you will compare the resulting water colour against the colour charts.

It’s important to remember that reagents have a limited shelf life for most effectiveness. For instance, pH lasts up to two years, while other reagents may not last as long. For this reason, plan to purchase a new test kit annually. You’ll feel better investing in this than taking on the expense of caring for ill fish or possibly replacing those that cannot live in their low-quality environment.

Pond Salt Meter
To ensure healthy water for your koi, you should purchase a salt meter. In the summer, the salt level should be 5ppt or .05%, whereas in the winter, salt water has a lower freezing point. Water will freeze driving up your salt ppt in the unfrozen water.  .15–.20%. This difference is required to reduce the osmoregulation drain on your fish.

Meters
As a serious koi hobbyist, you will no doubt want to include an ORP meter in your toolbox. This oxidation reduction potential provides an accurate snapshot of your water quality. Higher ORP readings result in cleaner water. A lower ORP reading may be the result of poor filtration, low dissolved oxygen, or abundant organics.

In addition, ORP meters are a useful tool for correcting the dosing of potassium permanganate, especially when judging the water color gets challenging during the second and third treatments.

Nitrification: The Key to Quality Water
Ammonia
Ammonia, or NH3, is produced by both fish and decaying matter. In even minute quantities, at .25 mg/L, it is toxic. Its presence can result in damaged gills, skin, and red blood cells.

Cold water, on the other hand, creates an environment in which ammonia is up to three times less toxic. That’s because nitrifying bacteria do not function in colder temperatures. Less NH3 is ionized into ammonia, leaving more free ammonia, in a higher pH because fewer H+ ions are available.

Total ammonia nitrogen (TAN) toxicity is more problematic with higher pH levels in which fewer H+ are available to bind with NH3. With more H+, NH4+ is created, which is not toxic.

Nitrite
Nitrite, chemically known as NO2-, can take eight weeks or more to cycle, making it a stubborn issue. The bacteria grow better in higher pH and with lower salt content and require temperatures higher than 15ºC. At times, they have been found to grow at 12ºC with established filters. In addition, they need phosphorus to form ATP and carbon dioxide to gain carbon.

Nitrite poisoning, also called methemoglobinanemia or brown blood disease, restricts the blood from carrying oxygen efficiently.

Nitrate
Although nitrate, or NO3-, is much less toxic than NH3 or NO2-, it becomes an immunosuppresent in fish, leading to diseases and potentially death. It also promotes lethargy, jaundice, and even blindness at high levels, and it slows growth. Naturally, tap water has NO3- levels of around 12.5 mg/L, and the water can be as high as 50 ppm without raising too much concern.

How to Improve Water Quality
Maximize Aeration
Maintaining a high DO saturation level is imperative to avoid ammonia and nitrite. The water should be kept at the ideal temperature as well, since the warmer the water, the lower the saturation point. That can lead to fish not being able to carry sufficient oxygen in their blood.

Add Salt
Salt provides the benefit of transforming ammonia, a toxic agent, into ammonium, which is not toxic. It also limits the amount of NO2- that gets into the fish’s blood stream. The water should have a saline level of at least .12%, and .20% is better when higher levels of NO2 are present. Remember that increasing salt is not a long-term cure, but it can provide a cushion of time during which you can really address the issues.

It’s important to note that salt levels higher than .10% can damage sensitive plants such as hyacinths. Also, salt does not evaporate. Consider using a salt meter to ensure proper salinity levels.

Reduce Feeding
Rather than feeding daily, switch to once or twice a week and use food with a lower protein level. When feeding more often, only about 40% of the food is digested. The higher protein food will also increase NH3 levels.

Use Ammonia Binders
Adding CloramX to the water will instantly destroy ammonia. The chemical is safe for fish and is an excellent short-term solution. If the ammonia level in the water is extremely high, binders won’t attack all of the NH3-, but the levels will improve greatly.

If you choose to use ammonia binders, you’ll need to alter your reagent choice. That’s because nessler-based reagents ignore the binder, resulting in the same toxic reading as previously. Salicylate-based reagents read the binders, while will provide an accurate reading. Nessler reagent charts are brownish in color, whereas salicylate reagents have a yellow and green color chart.

Increase Filtration and Reduce Fish
If ammonia is an issue, it’s important to remember that the fish themselves are contributing to the problem. Nearly 60% of the ammonia in the water comes directly from the fish when they are breathing. By increasing the filter’s capacity or reducing the amount of fish in the water, you will realize an immediate improvement in the water quality.

Small-pressure filters should be replaced with trickle towers or rotating media filters. With the proper size filter, a maximum of three pounds of fish per 100 gallons is suggested, although as little as one pound of fish per 100 gallons is reasonable. For a point of reference, a 12-inch fish weighs in at about one pound, and an 18-inch fish is about three pounds.

When judging the weight of fish, evaluate the number of fish in addition to their sizes. It’s inaccurate to use an “inches of fish” calculation since one four-inch fish will have a very different mass from four inches of a 20-inch fish. Focus on the mass rather than the inches.

Change the Water
One of your first thoughts in attempting to improve the water may be to change it completely. However, oftentimes, changing the water doesn’t have a long-term effect on the levels. The fish themselves can store up to 30 times the nitrite in their systems, which will return to the water following the change. Instead of trying new water, a better solution might be to add plants.

Filter Bacteria Keys
Maintaining proper alkalinity levels is key to healthy water. In addition, you need plenty of oxygen, aeration is imperative, and bicarbonates are essential for nitrification. To test the water, use the tetra KH kit. You’ll want to test at least five drops of water before you see a color change. That signifies almost 90 degrees German hardness, which is the proper buffering level. It can benefit the fish’s skin to have lower alkalinity levels, but you will need to increase your monitoring and have the skill needed to avoid a pH crash. For that reason, less than 50 ppm content isn’t practical for most fish keepers.

To quickly boost KH, you can add baking soda, which is sodium bicarbonate (NaHCO3), but you will need to watch the pH change. Adding ½ cup of baking soda to 1,000 gallons of water will result in a .5-point pH increase and 1 degree (or more) of KH hardness. If your pH is 7.1, for instance, you want to add the sodium bicarbonate gradually; otherwise, you’ll be dealing with a rapid pH change. No matter what the pH was initially, adding NaHCO3 will buffer it to 8.4.

Manage the Temperature
It’s important to keep the water’s temperature at an optimal level. Higher than 21ºC / 70ºF is ideal for bacteria growth and the koi’s immune system. However, the warmer the water, the higher the toxicity of ammonia and pH level. Your goal will be to have the temperature in the right window for health and bacteria while curbing a toxic increase of NH3.

Bio Seeding for New Pond Syndrome
A new pond will normally go through spikes in ammonia and nitrite during the course of the first 8 to 10 weeks. It can then take years for Kaldnes and Japanese matting to fully mature within the system.

If you are considering bugs in a bottle, it can be a very hit-and-miss solution. Most koi keepers do not employ a scientific method when dosing, leading to variable results. The best way to use this approach is to capture the dirty water from squeezing out the seeded filter media from an established filter system. Place this water in the filter while it is turned off. Then wait 20–30 minutes before turning the filter back on. This method will fast track the maturity of a new filter, leading to better results.

Green Water Is Good Water
One of the best ways to help turn around poor water quality is to turn off the UV and let the water turn green. Turning off the UV stops killing bacteria, although nitrifiers are bacteria that attach to surfaces and are not free floating. If they aren’t planktonic, they won’t go through the UV filter.

You want to encourage algae because they consume nitrates and ammonium. Equilibrium occurs (NH3 + H2O = NH4+ + OH-) between ammonium (NH4+: safe for fish) and ammonia (NH3: a toxic gas). When algae eat ammonium, ammonia is ionized to the harmless ammonium to maintain nitrogen equilibrium. There is a corresponding drop in nitrites as well due to the fact that NH3 produces roughly the same amount of NO2 during nitrification.

Complete Water Testing at Your Place or Ours
Water quality can change quickly, so you should be testing yours twice a week at a minimum. You cannot rely on visual inspections alone, as fish can often look healthy even in toxic water. By the time they look unhealthy, the problem could be a lot worse and harder to turn around.

We can test your water at the store when you bring it in, or we can test it at your location during a routine house call. Contact us to learn more.

Picture by Jeffrey Tucker