The general health & well-being of Koi in a pond is directly related to the quality of their environment. The better the water, the healthier the fish will be. Healthy fish will feed readily, be active in the pond, and have good skin lustre. A pond with inadequate filtration & high ammonia levels will result in fish that become sick and fall prey to parasitic and bacterial infections. Heavily stocked ponds will also stress the fish population.
Once you have kept Koi for a while, your fish will let you know that they are sick. Koi that go off their food, sit at the bottom of the pond, or have their fins clamped to their bodies are sick. If the oxygen levels are depleted, fish may gasp at the surface for air. Sometimes fish that are infected with a parasitic infection such as Costia will swim at a strange angle.
The best remedy is to ascertain what the root cause of the problem is. The first step should be to check the water for Ammonia, Nitrite, Nitrate and PH. If any of these are incorrect, then a water change is advised. Should the PH be too low, the fish will stop feeding and can go into PH shock. The addition of Sodium Bicarbonate will correct low PH. Ponds that have a fibre-glass lining often tend to exhibit low PH.
Should all these tests be within acceptable levels, then one should check for any parasites which may be present. With a few exceptions, these can only be seen by examining a scraping from the fish under a microscope. If you do not have access to one, then your reputable Koi dealer will do this for you and advise on the best medication. Most preparations involve treating the whole pond, while bacterial infections can be treated with an application of topical medicine as well as anti-biotics. These can either be injected or mixed with food. One should remember that all medicines are really poisons of some kind, therefore it is important to ensure that the medicine used is the correct dosage for the pond volume as well as being effective against the particular disease. An overdose or the wrong medicine will kill fish quickly. In most cases, the Koi will have a better chance of survival if they are kept in their big pond where the water is properly filtered, than if they are transferred to a tiny bath or bucket. Treating the whole pond will eliminate any problem in the water.
As important as keeping the pond environment healthy, is the correct feeding of your collection. In the wild Koi have a varied diet, feeding on small insects, worms and water organisms. In our ponds we need to try to give them as close to what they would eat in nature. Good brands of Koi pellets will have a fairly high protein content 35% – 40% and supply all the essential lipids, carbohydrates, vitamins and minerals. Check to see that what you are feeding does not have a low Protein content – below 35%, and that it smells fresh. Stale or mouldy food is harmful to your precious Koi. There are excellent quality locally manufactured Koi pellets, as well as imported brands available.
Koi have a digestive tract rather than a proper stomach, so can only absorb a certain amount of food at a time. Koi will benefit from more frequent feedings of smaller amounts of food during the day. The amount fed largely depends on the number and size of the fish in the pond. Overfeeding will put a strain on the filter system as well as resulting in cloudy, unhealthy water. Remove any uneaten food after 5- 10 minutes, and give a little less at the next feed.
Koi feed vigorously in the hot summer months. As autumn and winter approach the feeding will slow down. Along the coast in Kwa Zulu Natal, Koi will feed throughout the year, taking perhaps only a little less during winter. Inland where water temperatures drop below 12 degrees, Koi will go into a state of hibernation and stop feeding altogether. If your water is very cold, do not be alarmed should your Koi lie at the bottom of the pond and sometimes even fall over – they are literally just “chilling-out”