What is the Best Koi Pond Alkalinity Level?


Generally levels of 50-170 are what is recommended although some Koi keepers are keeping their pond levels already higher at around 180. The reason for this is that alkalinity will decline over time as the good bacteria in your pond consume bicarbonates which slowly decreases alkalinity.

Alkalinity can also be referred to as carbonate hardness or German carbonate hardness. It is the measure of the concentration of the capacity a solution has to neutralize acid without changing pH. It both maintains and controls water pH. Koi pond alkalinity level can be measured in parts per million of calcium carbonate (ppm of CaCO3), milligrams per liter (mg/L), grams per cubic meter or degrees (dKH).

Test kits measure alkalinity as carbonate hardness or dKH and often in degrees of German Hardness (odH).If you want to transform German Hardness to parts per million (ppm) you can simply multiply by 17.

in spite of of the fact that that a pH of 7.4 is best for Koi fish it can be a good idea to keep th pH level a little higher. pH levels can crash quite quickly when your alkalinity (KH) begins getting lower than 80 ppm. Since alkalinity is the buffer that helps continue pH it is important to test it regularly. You may find that it’s better to keep your Koi pond alkalinity level above 100 or 120 pm. It will give you a bit of a buffer zone to help continue your pH.

There are several ways that you can add alkalinity to your pond.  One way to do this is by water changes. This can help introduce new minerals and can also increase alkalinity. However, if you have softer water it’s alkalinity can be less than 80 ppm. You can increase both the pH and KH by adding Arm & Hammer Baking Soda to the water. One third cup of baking soda per 1000 gallons of water will raise the KH level by 25 ppm.

Make sure that you take care not to raise the KH level more than 25 ppm a day. If you do it will cause undue stress to your Koi. An exception to this is if you are losing fish to a pH crash. A pH crash is when the pH level hits 5.5 or lower. In this case you have nothing to lose by adding a bit more baking soda to the water.

Water doesn’t have to have a high pH to have high alkalinity. Alkalinity is related to the dissolved amounts of calcium, magnesium and other compounds in the water. This is why alkalinity tends to be higher in hard water as opposed to soft water.

There are various reasons that Koi pond alkalinity level will decline over time.

Decreases occur naturally over time due to bacterial action which produces acidic compounds which combine with and decline alkaline elements.

Ponds with fiberglass construction or vinyl liners tend to characterize a higher decline in alkalinity over time and might need supplementation to help them continue proper levels. Alkalinity can be raised by adding calcium carbonate, oyster shells, concrete blocks, egg shells or limestone.

High alkalinity can be prevented by ordinarily changing out the water if the water you are replenishing with has a lower alkalinity than the pond water.

An established pond usually maintains an equilibrium in it’s pH value if you keep it clean by removing sludge and any organic materials before they have time to decay. Scheduled water change outs (i.e. 10% / week for small ponds, less for larger ponds) can also help continue proper pH and Koi pond alkalinity level.

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