Just as we need clean and fresh air for our good health and survival, koi need clean and unpolluted water to do well. This is the single most important factor for koi to thrive. Realising this, we should do our best to provide good clean water for our beloved koi. This simple and most basic requirement is often overlooked and taken for granted. It is not easy to maintain good water quality throughout the year. This is especially so in a densely stocked outdoor pond that is also subjected to the elements. Fortunately, we do not require expensive or very high tech methods to keep water good enough for our koi. All that is needed is just a good understanding of the basic concepts of water filtration and recycling. With this knowledge, one can begin to construct a filter that will provide good water for his pond and koi. A koi that feeds aggressively and growing well is a healthy koi. In fact the earliest sign of a serious trouble in a koi would be the reluctance to feed. All my koi would be swimming close to the surface at the feeding spot when they see me. Prior to feeding I would look around (I could see right to the bottom) to see if any koi is not showing any interest like the others. If there are any, I would observe them closely. If all are well, there shouldn’t be any koi remaining stationary at the bottom or staying away from the others. You could say that koi communicates with us by way of their behaviour in the pond. If you see your koi suffering from some illness one after another, you should begin to suspect that there is something wrong with the water and should go about to investigate.
Besides a good filtration system, water quality can also be affected by our feeding practices and the stocking level. If the filtration capacity of any pond system is already at it’s maximum, the stocking level will be inversely proportional to the amount of feeds if good water is to be maintained. The temptation of keeping more koi and overfeeding are always there. This will ultimately lead to deterioration of water quality and the koi will begin to suffer from all kinds of illnesses. In overstocked ponds that are able to maintain good water quality, the koi are healthy but maybe stunted or have low growth rates. Feeding koi is a very enjoyable thing to do. I must say that I still feel the excitement each time I feed my koi. However always bear in mind that the water quality comes first. What is missing a feed or two if it is to ensure that good water quality is maintained and ultimately for the good of the koi? Koi are hardy and are able to withstand quite long periods of starvation. Morever there’s plenty of algae in the pond for the koi to feed on. Therefore, we should not look at feeding as the most important thing but rather as second to having good water. Good quality pellets should be used. They should be digested completely. The faeces should also not breakup easily and foul the water. Overfeeding can cause faeces to contain undigested food which may decompose or act as source of food for bad bacteria. Therefore feed just enough so that each koi would have taken in a few pellets. This should not take more than 5-10min. Remember that feeding a little at a time at regular intervals is cleaner than feeding a lot but only once or twice a day.
Water may be examined grossly with the naked eye, microscopically with the microscope and chemically with reagents. The most important factor is the chemical composition of the water which will affect the koi immediately. Ammonia, nitrite and chlorine are the commonest invisible toxic substances that a koi may encounter daily. Other dissolved substances that will affect the health of the koi are the pH buffering ions like calcium, magnesium, sodium, chloride, carbonate and bicarbonate ions. Particles suspended in the water which are visible to the naked eye includes algae, debris and wastes.
Most people tend to think that clear water is synonymous with clean and safe water for koi. In their natural environment, or in the mud ponds, koi still do very well inspite of poor visibility caused by the suspended mud particles. From here we can only deduce that the chemical constitution of the water is good and free from toxins. On the other hand, we hear of koi dying or developing diseases eventhough the pond water is clear. There may be something invisible to the naked eye that caused the disease. The point I am trying to make is that clear water does not necessarily mean good water. Every koi-keeper should have this in mind and should strive to first of all maintain a chemically safe water for koi. Safe water should be a top priority and should be mastered by every koi-keeper. Having done so, one can go to the next stage of striving to have clear water in order that the koi are nicely visible and enjoyed.
Hardness (General Hardness or GH) is a measurement solely of the minerals in the water, which primarily include Calcium and Magnesium. Alkalinity is a measurement of the carbonate activity in the system and is often expressed as KH (Carbonate Hardness) which is an unfortunate and confusing misnomer. One can raise hardness to dangerous levels and not increase the pH because minerals in general do not change or stabilise pH. Indeed, the molecules usually associated with the minerals do. For example, by adding calcium and magnesium carbonate, one would be supplying calcium and magnesium, boosting hardness. The carbonate fraction would contribute to Alkalinity. Therefore by adding baking soda or sodium bicarbonate, one does not raise water hardness but raises the Total Alkalinity or pH instead.
I am fortunate to live in this part of the world where the municipal water is of reasonably good quality. I do have a dechlorinator that is large enough to supply the whole house with filtered and dechlorinated water. Rock salt is added occasionally to maintain salinity between 0.05% to 0.1%. I believe a mild salt solution is beneficial for koi. I find that wounds like small bumps and scrapes that my koi accidently sustain heals faster. The pH of my pond water is slightly higher than my tap water supply. This level of pH is good enough for koi. It maintains the Hi and at the same time good enough for Sumi development. KH is also slightly higher than that of tap water due to the concrete pond. I do have some cockle shells in the last chamber to raise the GH a little bit. I used to add bentonite clay into the water as a source of minerals but noticed that algae growth was increase as a result of increased phosphate level in the water. I have stopped this practice eversince and the algae is under control. Temperature does not fluctuate much throughout the year in South East Asia. As a result koi grows throughtout the year due to the same feeding regime. My pond water nitrate levels are never below 10ppm. I’m not worried about nitrates because they are not harmful if kept below 50ppm or so. In fact, the plants will not survive at low nitrate levels. Ammonia should of course be undetectable at all times. A word of caution about ammonia. It is more toxic at higher pH because more non-toxic ammonium ion are converted into toxic ammonia. Nitrite level should also be undetectable but upto 0.25ppm is tolerable. Nitrite is the result of nitrification of ammonia by Nitrosomonas. This reaction consumes carbonates. Nitrite is also toxic to koi and is often termed the invisible killer. Alot of times, we only pay attention to ammonia but neglect the nitrite levels. In actual fact we should be more vigilant against nitrite because the nitrobacter that converts it to non-toxic nitrate are fewer and the energy available for conversion is now less after the ammonia-to-nitrite stage. Hence, it is not easy to convert nitrite to nitrate. In a new filtration system the nitrosomonas are established faster than the nitrobacter. Therefore the initial rise in ammonia will be followed by a drop. This will be followed by a rise in nitrite level. If we ignore nitrite at this stage, and think that our filter has matured and so we feed more or add more koi, we are heading for trouble. This is because the resulting nitrite spike will kill the koi or cause serious injury to it. A common indication of a koi that has endured a severe nitrite spike in the past is that the gill covers may be slightly rolled outward at the edges. They do not close flat against the koi's body. Similarly, when doing large water change outs, alot of nitrobacter bacteria may be lose and a nitrite spike may occur. The obvious measure taken to prevent this would be by reducing feeds a few days prior to and after the water change out. Dissolved oxygen levels should be adequate eventhough not actually determined. I have 2 venturi and 3 waterfalls to supply plenty of oxygen. My koi are active and hungry throughout the day. They stay at the bottom during the night.
PH : 7.4 to 7.8
KH : 5-6 dKH or 90-107ppm
GH : 4-5 dGH or 72-90ppm
Temperature : 24 to 26 deg C
Salinity : 0.05 to 0.1%
Nitrate : 20 to 30 ppm
Nitrite : undetectable
Ammonia : undetectable
DO : unknown
Additives : rock salt -6 monthly to make 0.1% salinity during filter maintenance. : baking soda -very rarely. : bentonite clay –not anymore.