When it comes to growth rates with koi there are several things that play an important role but in the end it comes down to trying to keep your koi in the best condition possible. I have tried to highlight the most important factors to achieve good growth rates in the section below in the order of their importance. Pond Volume and amount of Koi in pond.
This is the most important factor. Your fish will have to share all the resources in the pond. So the less fish you have in the pond or the bigger the pond volume the less the fish will have to share...All the other points that follow are secondary to this rule.Oxygen.
Oxygen is the most important of the secondary points. It helps with the growth of the koi and helps to have a general healthy pond. A lot of problems can be solved by just adding more air into the system. The surface area of a pond plays a very important role as it is the lungs of the pond system, it is the area where the transfer of gasses takes place and so a large surface area is beneficial to healthy koi pond. Filtration.
It is pointless to try and feed koi lots of food if the filtration system is incapable of handling the waste. So make sure that the filtration system is up to scratch.Water temperature.
Warmer water will cause the koi to be more active and to eat more. It is during the warmer months of the year that the koi eat and grow the most. If it is possible to heat and maintain your pond at a temperature of at least 18*C during winter you will have much better growth rates than the rest of the koi keepers that do not heat their ponds. Another tip is to try and manage the temperature of your water through the means that water returns to a pond. In winter a pond with a waterfall will have a lower temperature that a similar pond with underwater returns, this is because the water falling from a waterfall will be chilled by the cold air. It would be beneficial for koi keepers in cold area to build their ponds in such a way that they can switch over to underwater returns during winter and by so doing help to keep the pond temperature higher.Variety of food.
This is probably the second most important factor in obtaining good growth rates. Feed a high quality high protein food as the basic diet during summer. Depending on your area it might be possible for you to feed high protein the whole year long. When the water falls below 18*C it is a good idea to add some 50% wheatgerm to the koi diet. During the year you can also give the koi a variety of other treats...like worms, prawns, oranges, bread with honey, cabbage, rice and so forth...A well balanced diet will increase the health of the koi and assist them in growing bigger. I believe in feeding blood worms during the months of Aug to December especially to tosai when the water stars to heat up, and i have seen how to koi grow during those period. Check out this
article. Amount of food.
Feed several small portions many times a day.Water changes and Cleaning of filters.
Water changes are important because it creates the illusion that the fish are in a natural system where fresh water is flowing into the area continuously. Replace a minimum of 10% - 15% weekly and will be achieving this goal. Larger koi releases growth restricting hormones into the water especially in over crowded pond. These hormones restricts the growth of smaller koi, by doing regular water changes you will keep the hormones to a low level and aid in the growth of the koi. Water changes can easily form part of the weekly filter system maintenance.Turn over rates.
The faster you can turn the water over in the pond the better the quality of water is going to be. The term "turning the water over" revers to the cycle in which the water leaves the pond and passes thought filtration system and pump and returns to the pond. The koi keepers should aim to turn the water of his pond over in 1 hour. Removing of Organics.
Organics can play a role in the growth of your koi so remove it as regularly as you can. Organic waste is usually visible as white foam that collects under a water fall. These waste products can hamper the growth of koi. The best way to remove these waste products is by means of a protein skimmer.Pond Depth.
There is lots of ideas and stories about what role depth plays but from what i have seen in my pond i can say the following..Depth helps to have more constant water parameters and water temperature and helps to develop the desired body shape of koi. My personal pond slopes from 1.2m to almost 3m. That means that the koi are constantly exercising because they are swimming up and down the length of the pond the whole day long.Top up water and Minerals.
Novice koi keepers try to keep koi by in plain unfiltered tap water. Tap water contains chlorine, ammonia and chloramines. Tap water is in fact dead water like in a swimming pool. The Quality of tap water is different from one area to the next, so care should be taken to Annalise the tap water and to determine what the tap water quality is like. Municipalities usually add chlorine to their water supply to try kill all the bacteria in their water supply and by so doing improve the drinking quality of their water but because chlorine evaporates quickly they add ammonia to the water as well. Ammonia and Chlorine combines and forms chloramines. Chlorine, Ammonia and Chloramines are deadly to koi and care should be taken to remove these items from the water supply. This can be done by installing a simple in line water filter.
The Total Alkalinity of the tap water should also be measure as tap water tend to have very low Total Alkalinity level which would affect the kois development. Total Alkalinity is a used to test the intensity or hardness of the water. Tap water with a low Total Alkalinity will result in a PH swing in the pond water which is dangerous to koi. A High Total Alkalinity helps to create a more stable PH and It is also interesting to note that a higher Total Alkalinity will help to finish the colours of a koi by bringing the black out.
Tap water usually does not contain the minerals found in nature which our koi would need. Montmorelite clay need to be added to the water to put the lost minerals back. Add montmorelite clay to a pond at least 1 a month but it is best to add a bit every time a water change is done.Day Light.
I don't think that many people realize what role light plays in the growth of kois. The fact is that as long as there is light on a pond, koi will continue to be active and will continue to feed. So you can extend the feeding time of the koi simply adding a spotlight to a pond.Current.
It is important to have current in a pond. Koi must have a stream of water to exercise against. This again helps to build the muscles and overall body shape of the koi. A lot of pond are designed with only waterfalls or gravity type returns and one you can note that koi in these ponds appear to be fat and bulky. You need a return below water level to create current. Some koi keepers have several underwater return that activate by means of a timer device, these returns change the flow of the current in the pond and give the koi even more unexpected areas to exercise against.Rest.
After all the eating and exercising your koi will be in need some rest. Do not disturb your koi during the night. Try to minimize the water movements in the deeper part of the pond during the night.
As you can see from all the points above, Good growth rates can be obtained by the general conditioning of the pond.This is from an article on my website which can be found here.