About 8 - 10 years ago I really battled to get good growth out of my koi collection. The reason? - The high cost
of koi food. This statement is not pointing finger or sarcasm, but it is an inescapable fact. If you have a large number of koi and you feed them well, it will cost a lot of money. But you will get growth.
I have never considered depth to be critical in achieving growth. The "deep" end of my previous main pond is
a mere 80 cm, which I admit is a little shallow when you see some of the koi from under water with goggles.
From a personal perspective, I certainly would not go deeper than about 1.2 meters at the bottom drains in
any pond where koi are to be viewed. The size, 30 koi in my collection grew too, in a relatively short time
span, is proof enough to me that depth is not a critical factor in achieving growth.
I am absolutely convinced beyond a reasonable doubt that to achieve good growth in a koi collection five
critical factors are needed. Good quality water (filtration etc.), high oxygen levels (high turnover rates etc.),
regular water changes (at least 10 - 20% per week), warm water temperatures, and most importantly, large quantities of good quality food. Throw in some good genetics and a little luck and you will get good growth
without very deep and very large ponds.
Source references state, that to get high growth out of koi (carp references) they should be fed about 2% of
their body weight per day. Some years ago the 30 koi in my main pond of 18,000 litres were measured in an attempt to calculate body mass. My calculations arrived at a figure of a total mass of about 80 - 85 kg for the
At a feeding rate of 2% body weight per day, this group of koi would need to be fed 1.5 – 1.7 kg of food during
the course of each and every day. It does not take a rocket scientist to calculate the high cost of the total
volume needed to be fed to the collection. I then realised that because good quality foods are expensive, koi keepers tend to under feed their collections on quality nutrition and therefore do not get the growth they could possibly achieve.
In my old pond I achieved growth rates, of up to 75cm in four years. Annual water temperature varied from
about 25°C for a number of months in summer to a few weeks at 9°C in the middle of winter. Water changes
were at least 20% per week. The turnover rate was the total volume of the pond through a single chambered
filter in under an hour.
When I made a conscious decision to manufacture my own koi food for the retail koi market, I took a long hard look at the Japanese koi foods. Also an animal nutritionist was consulted, a really good lady, down to earth, brilliant and very well connected in the animal nutrition world. Computer technology was also employed.
The koi food I manufacture gets koi to 25cm in a year from hatching and closer to 30cm at coastal regions,
where temperatures are warmer through out the year. So I would like to share with koi keepers my experiences and some of my intimate knowledge on koi nutrition.
What Koi Need in the Diet:
Endless articles have been written on “what koi need in their diets”, what should be present and what should
not. Hundreds of articles simply repeat and rehash what has already been written so many times
It is a fact that Koi need a high protein diet. High protein can mean anything so we must define it. 35 -38%
protein, is the minimum requirement for the koi diet.
Some koi keepers advocate reducing the protein level to around 30% when the koi is about 5 or so years old.
As koi keep on growing past the age of 10 years old, it makes sense to continue with the 35-38% protein level. Skin quality benefits, as does health.
More important than protein levels are the balance and level of the amino acids. Incredibly a food can have a
high protein level but be low on specific essential amino acids. The result, the whole formulation does not work well. Amino acids are the building blocks of protein. The body cannot absorb protein as such. So protein has to be broken down, through enzyme, action into individual amino acids. These are then absorbed, transported to
the cells where in conjunction with other nutrients are reconstructed into body protein. Irrespective of the source
of protein the body breaks the eaten protein down into amino acids.
Some koi keepers advocate changing to a wheat germ food in winter. Some koi keepers continue to feed the same food through out the year, reduce the quantity as temperatures drop and stop when water temperatures
fall below about 10 - 11°C.
Analysis, of pure wheat germ meal indicates that wheat germ contains many of the same amino acids found animal protein sources, albeit at a lower levels, than say raw fishmeal. So although the one food has wheat
germ as a protein source and another may have fish meal as a protein source, when enzymes process the
protein source, the net result is - the same basic amino acids in the stomach-blood-cells, chain.
Many high quality koi foods use a fishmeal as the major protein source simply because many of the nutrients needed by koi (amino acids, lipids, vitamins, minerals) are found in this food source. Fishmeal is often is short supply around the world, resulting in rocketing prices in the last few years. Fishmeal has around 60-65% protein
in its raw state.
Lipids are essential in the koi diet. They are a very good source of energy and certain oils are essential for the cells. As protein can be utilised by the body for energy the addition of lipids are very important as they act as a protein saving ingredient. Protein is then used for growth and tissue repair while the lipids are used as energy sources. Koi can utilise up to a 12-13% lipid content. However, the oil/lipid percentage in koi food is generally
at a much lower level. The reason for this is quite simple, shelf life. Oils can and do go rancid and cause the
food to go bad. Rancid food is not good for any animal not least the koi. Free radical activity in rancid food
can be retarded and checked by ingredients such as Vitamin C and Vitamin E.
Freshness is important for koi food. However, it is a fact that most imported koi foods are at least 4 months old before they get to the koi outlet shelves. There is no way around this. From the date of manufacture the food is
not immediately bagged and transported to the dealer and end user in another country. Factories need to have very large production runs to make koi food cost effective. Not every kilo of food is sold immediately. There will always by some storage time. Add to this a few weeks to pack and containerise the food, followed by transport
to the coast and time spent at the docks. The container is a few weeks at sea. The food then takes time to clear the destination docks at the respective country of import, (if there are no strikes) to further delay transport of the goods. The food now has to get to the distributor where further storage time is needed. Then eventually to the retail shelves.
In formulating the food these factors are usually taken into account by the manufacturers of the better quality koi foods. Preservatives, both natural and artificial are used. Quality vitamin premixes are added to the food before manufacture to accommodate the heat loss during the extrusion process and to compensate for shelf life degradation of ingredients. As an example, an analysis of high quality food of at least 6 months old should still indicate a high level of Vitamin C. Some years ago Vitamin C used to degrade rapidly after manufacture.
Within 90 days of manufacture about 50% of the Vitamin C was degraded. Through scientific research a stabilised form of Vitamin C is now used which lasts just as long as most other vitamins.
A formulation of around 35 – 36% protein would need only around 28 – 30% fishmeal (remember raw fish meal
is 65% protein). Many formulations use a combination of ingredients to get different levels of nutrients in balance and the right quantities. So once we have the important protein level plus some lipid, vitamins, minerals, preservatives we are left with around 30% of the total volume of something – this something is carbohydrate.
We are now faced with a unique situation in the animal kingdom – to deliver the food to the gut of the koi in a water medium.
No matter what we think or want or have been told, at this point in time virtually all koi foods have around 30-35% carbohydrates. Why? Firstly carbohydrate is not a bad ingredient. Carbohydrates are an energy source and do contain some nutrient needed by the body. Carbohydrates are digestible after cooking via the extrusion process, and koi can digest carbohydrate quite well.
Protein can never be 100% of the formula. Nor can the other ingredients. In order to arrive at a nutritionally balanced koi food formula we have to have certain ingredients in appropriate proportions. So in order to make
up the remaining percentage to 100%, carbohydrate is added. But there is a more important reason for carbohydrate in koi food.
Carbohydrate is the medium in which the nutrients are delivered to the gut of the koi. The proteins, oils etc,
need to be delivered to the stomach of a koi. We cannot just put down a bowl of food in the pond and wait for
the koi to eat it when they want to, for obvious reasons. The aquatic environment presents unique difficulties.
So we have to literally trap or glue the nutrients together so that they can get into the stomach of the fish with out dissolving in the water.
Now that we have a nutritionally balanced pellet for our koi – how do we achieve growth? Referring to my
opening: – the factors producing growth in koi are - good quality water (filtration etc.), high oxygen levels (high turnover rates), water changes (at least 10/20% per week), warm water temperatures, and most importantly, large quantities of good quality food. Throw in some good genetics and a little luck and you will get good growth
without deep and very large ponds.
With the above factors in place, we must feed koi regularly several times a day. In tests at carp farms it was demonstrate that up to 60% more growth was achieved when the fish were fed three times a day as opposed
to once a day.
But there is another factor I discovered a number of years ago. Dampen the food you are going to feed the fish. I do not have scientific proof, only my own observations, butI remain absolutely convinced that by making
the pellets damp that you are going to feed the collection that day, you will achieve better growth. Do not float
the pellets for long periods; you will loose essential water-soluble vitamins. Merely dampen the feed for that day. You will notice that the koi can literally suck in numerous pellets at a time. Normally with dry pellets they take in
one or two then head off to chew them. But with dampened food they consume more and young fish can be fed
on the same size pellets as the large koi.
Just like our children, koi need the correct nutrition over a sustained period of time, but more so in the early
stages of its development. If nutrition is poor in the development stages of a creature’s life, there is simply no
way to catch up or repair the damage. The creature will remain stunted and underdeveloped.
An American Experiment:
Some years ago Andy Moo wrote in Koi USA that he achieved 23cm of growth in his koi in 6 months. What was fascinating in his article is that he stumbled upon the growth by accident. Initially, Andy kept seventeen 10-13cm koi in a 1500 litre show tank. He noticed that the fish always appeared hungry so he gave them a light feed every time he walked past. Much to his surprise these fish grew from their original size to 25-33cm in less than five months.
Excited about his "discovery" he followed the initial results with several other tests. He chose 45 x 10 - 13cm "leftover" koi from his opening sale. These koi were placed in to his lily pond that is only 30cm - 60cm deep and has 5000 litres of water. Central to his experiments was the fact that he fed about 2% body weight per day. This was increased up to 4% body weight per day as the temperature increased in summer. He increased the frequency of the feedings from four times a day up to twelve feeds per day. Also central to the experiment was
a high water turnover rate plus a large and efficient filter. At the end of just 166 days the average length of the
45 koi was 36cm. These tests were done in what we would consider a limited pond size and shallow depth.
Andy observed that overall body conformation was excellent with none having potbellies, and with a few exceptions their colours did not fade but had actually improved.
If Andy can achieve growth like this in a relatively small pond, so can the rest of us.
In their natural environment a koi's intake of nutritional substances is extremely wide and varied. In some unsympathetic quarters, carp are often referred to as the 'pigs' of the fish world. Their ability to consume
and assimilate virtually anything has accorded them this indignity. We can use this fact for our own advantage.
In nature koi consume small amounts of food continually throughout the day. Nutrition plays a vital role in the
health of koi. Koi are generally kept under artificial conditions i.e. closed circuit limited volume ponds, most of their natural food supply is also cut off. Therefore, whatever we feed our collections the basic rule must be -
A varied diet together with as much live food as possible should be given.
Last Updated on Thursday, 16 April 2009 21:37