Alkaline Koi Ponds
Generally speaking, alkaline conditions are more common than acidic in ponds, especially the newer ones. If the pH remains over 8.5 for any length of time, the koi fish will become stressed or diseased. Here are some helpful examples:
• Lethargic or listless fish due to damaged mucus coating; prone to fungal
infection and other disease
• Plants chalky in appearance due to calcium deposits
• Prominence of waste chemicals which harm pond life
• Biological filter loses effectiveness
• Introducing fish too soon into a newly constructed pond that was not properly sealed; the lime or alkali from the cement will raise the pH to the top of the scale. Even a shovel full of concrete or mortar can cause serious problems.
• Lime leaching from cement products such as blocks, stepping stones and
similar materials over a period of time.
• Lime in stone products subject to erosion
• Excessive growth of algae.
• If the pond alkalinity is from the koi pond being new, allow adequate time for the pond to age. To speed up this process introduce bacteria found in a koi pond starter solution.
• Institute a partial pond water change to dilute the alkalis
• If high alkalinity is due to an over-abundance of algae, remove excessive growths of thread algae.
• If these steps do not result in a lower pH, use acidifying compounds or pond
Acidic Koi Ponds
Low pH conditions occur less often than alkalinity in koi ponds.
• Fish become stressed, resulting in sickness; they may start dying off.
• Oxygenating plants such as hyacinths, water lettuce, Elodea and Anacharis
become discolored and wilted.
• Biological filtration ceases to operate correctly.
• Pond water may have lost its buffers due to excessive amounts of rain,
which is soft and very acidic in many areas due to pollution. Loss or
decrease in buffering agents can create drastic fluctuation in pH.
• There may be high levels of humic acid or other organic acids produced
by build-up of decomposing plants and leaves.
• Regular partial water changes
• Adding buffers to pond by placing a mesh bag of oyster shell gravel,
dolomite or crushed coral gravel in filter or waterfall. Water passing
through the material will pull out the calcium carbonate and raise pH.
• Using pond-buffer salts (sold in pond supply stores)
Partial Water Changes
Wastes and toxins tend to build up in most ponds, despite use of a biological filter. As water evaporates, pollutants remain and build up over time, becoming dangerously concentrated. For this reason it is highly recommended for smaller koi ponds that you drain and replace 20 percent of the koi pond a couple of times a year. Larger koi ponds are generally much more stable and the water chemistry does not fluctuate radically. This water should be siphoned or pumped from the bottom of the koi pond, where the majority of pollutants collect.
No more than 20 percent should be replaced since larger amounts could easily upset the balance of the koi pond. This is especially true if the replacement water is softer or contains high levels of chlorine or chloramines. It would also be advantageous to keep most of the rotting debris cleared from the bottom. Decaying fish and pond waste produce ammonia, methane and other toxins which can be fatal to the koi pond family.
If you are adding water with a garden hose, it is best to adjust to low volume and a mist that sprays gently through the air before entering the pond. This will allow some of the chlorine to evaporate. If you add the water quickly, add a dechlorinating product to the koi pond to neutralize the chlorine and chloramines. Unless you are adding water to your koi pond by means of an electronic aquafill water leveling system, always use some type of a timer or alarm to remind you to turn off the water! If left unattended for an extended period of time, you could find your pond overflowing and your koi fish dying from chlorine poisoning. It happened to me… several hundred dollars worth!
Happy koi, peace & joy.