Establish a consistent maintenance program to promote stability and ease back pain. The design of the pond should revolve around ease of maintenance. If you set up your filter so it can be easily backwashed, you are more likely to do it religiously. What I see all too frequently is a pond which goes from one extreme to another, too dirty, too clean, too dirty, too clean. Letting the pond turn to garbage and then completely cleaning everything will never get you to the balanced pond you were hoping for. Alas, many pond and filter designs limit us to this kind of cleaning. Get the right filter design and you will be in charge.
Water Changes and Filter Cleaning.
Proper water changes are extremely valuable in maintaining stability. Tap water is totally different from your ponds water in pH, alkalinity, temperature, salinity, dissolved oxygen, it is sterile and contains chloramines. Make small water changes frequently. 10% water changes spread out more frequently are better than big water changes done infrequently. Don’t make big water changes unless absolutely necessary. Some emergency situations may indeed demand a large dilution. Toxic chemicals like pesticides or paint would require an immediate 70% to 100% water change to save the fish. A high ammonia or nitrite level would be better controlled with 10% to 20% daily water changes and corrective filtration principles.
In Japan the dealers provide a continuous drip or small stream of new water into the pond at all times. The pond continuously overflows via an overflow pipe. This drip may constitute a 5% to 10% daily water change. This,over time, establishes a very clean and yet stable water condition. Of course they are using well water. In other parts of the world we have too much clorine or cloramine to make this a feasible option. However, we can add up to 2% or 3% daily without dechorinating and without any harmful effect. In fact I know of a few ponds here in So. California using this approach with great success and nitrate readings as low as 20ppm with heavy fish loads. You will need an adequate overflow pipe to accomplish this successfully.
If you cannot use the drip approach you will simply have to change water when you backwash your filter. Crowded koi ponds or show koi displays may need 25% to 65% monthly water changes. Be careful of chloramine. Water gardens do not require large monthly water changes.
Clean your filters correctly and keep the backwash out of the pond. Use prefilters. Clean them weekly or more often. Clean biofilters gently and infrequently. Use multiple chamber filter designs.
Don’t mess with the pH too much.
Fixing “too high” or “too low” a pH can kill fish. Understand your reason for improper pH balance. Do not alter the pH by more than 0.2 increments daily. Establish a stable pH which your koi can live with. Somewhere between 6.8 and 8.2. Quite often, regular water changes will stabilize pH, however some parts of the country have poorly buffered tap water and you may need to add some type of buffer to the pond.
Don’t try to kill algae.
Algae is inevitable and desirable. Learn to appreciate algae. It is making up for lack of filtration. In some ponds algae IS the filter. Algae grows due to excess nutrients, sunshine and lack of bio-competition. Minimize algae occurrence with proper filtration and aquatic plants. Use enzymes, barely straw, shade;… non antagonistic methods. Use algaecides as a last resort. Ultraviolet sterilizers assist proper pond and filter designs.