Fried, scrambled, poached, or boiled (soft or hard). Eggs are such a convenient, tasty and versatile food that we can choose to cook them in one of many ways. And whatever form we choose to accompany our bacon, their nutritional content will largely be unaffected.
To some degree, the same can be said of koi foods. We can choose to feed our koi a number of different types of artificial koi food and yet all types can contain the same ingredients. In earlier articles in this series, we have concentrated on the ingredients and formulations used to provide koi with the nutrition they require. We have seen how the objectives of achieving health, growth and colour can be achieved by the selective formulation of a range of functional koi diets. We now turn our attention to the final link in the chain which is to ensure that the precisely formulated diet is made available for koi in a form that they can easily digest and assimilate. In doing so, our focus is switched from being concerned about the nutritional (or internal) details of the food to its external and physical attributes.
Having spent considerable time and expense researching the nutritional requirements of koi and their response to specific diets, a lot of this groundwork can be wasted if the food is not offered to the pond (and koi) in the most suitable form.
In the previous article, for instance, we saw how water soluble nutrients can leach out of foods as soon as they come into contact with water. Fish nutritionists, are aware of this and address the problem so that our koi do not receive a deficient diet. Consequently, the physical form of a koi food is of prime importance as it can have a profound effect on this and many other associated koi health factors.
Artificial diets can take many different physical forms and shapes with each type affecting its performance as a koi food. Artificial diets offer many advantages to the koi keeper and to a degree have become taken for granted as a reliable tool in the hobby. Yet without artificial koi diets, it would not be possible to keep koi in unnatural and heavily stocked ponds.
The benefits of an artificial diet.
1. Flexibility of Formulation. Unlike being constrained by the limitations of a natural diet, artificial diets can be tailored to meet any nutritional need. By manipulating the formulation and ingredients (which we are able to source from all over the world) it is possible to formulate an infinite number of diets. We can formulate for colour, growth, include additives to enhance health and even add medication to the food.
2. Precision Formulations. Unlike many natural diets whose quality is likely to fluctuate through the seasons and from year to year, artificial diets can be guaranteed to deliver precise nutrition throughout the year. They remove any unpredictability from the diet your koi are likely to receive.
3. Improved digestion and assimilation. Artificial koi diets can be compared to baby foods. They are highly processed, being finely milled and cooked, making them far more palatable and digestible than a raw and natural diet. Better utilisation of the diet by koi will lead to less waste being produced and better water quality.
4. Easier Feeding Although koi are bottom feeding fish, they can soon adapt to a floating pellet. This allows us to ensure that our ponds are not overfed and if ever too much food is offered, that it can be easily removed. Furthermore, a range of pellet sizes means that a range of mouth sizes can be catered for, ensuring that each mouthful contains a complete diet.
5. Long Shelf-life and Easily Handled The dry nature of artificial diets makes pelleted diets easy to handle and store. Imagine having to locate, store and feed daphnia or even maggots on a daily basis. They would soon deteriorate and prove difficult if not impossible to store long-term (and would not offer your koi complete nutrition). Dry artificial diets have a long shelf life (at least 12 months) and offer us unrivalled convenience.
Which Food Type? The different types of koi food can be divided into 3 groups.
Floating pellets & Sticks
Each food type offers a number of benefits to both koi and keeper, and can be considered for a number of practical reasons.
1. Floating pellets & Sticks
Floating pellets (or expanded pellets) are produced through a process called extrusion. Food ingredients are milled into a fine flour and heated into a paste which is then forced through a set of holes which determine the pellet diameter. As the warm paste is pushed through the holes under great pressure, they expand and take on air, creating a honeycomb of microscopic voids within its structure which makes the pellets light enough to float. A series of knives then cut this expanded sausage of paste into pellets which are then divided into the pellets we feed our koi. Floating pond sticks are made in a similar way where the knife cuts less frequently, producing a long stick rather than a more compact pellet.
Besides offering all of the benefits of an artificial diet as outlined earlier, pellets are also probably the best means of keeping leaching to a minimum. Due to the low surface area to volume ratio, pellets will absorb little water when consumed quickly, ensuring that koi benefit from a complete diet. Floating diets also allow us to interact with our koi and spot any individual fish that may not show an appetite. Thus feeding a floating diet can allow us to spot some health problems at an early stage.
2. Sinking Pellets.
A sinking version of a floating pellet can be manufactured in a similar way by preventing the pellet from expanding and taking on air during extrusion. As the resultant pellet is denser than water, it will sink.
Sinking pellets offer koi the ability to feed off the pond bottom (if the pellets actually reach the pond bottom before being eaten). They are a departure from the traditional floating pellet and should be used with care as any uneaten food may go unnoticed. Sinking pellets also do not bring the beauty of koi to the surface or allow us to see whether all koi are feeding. However, a sinking diet can be offered as a first food in the spring to encourage any reluctant feeders to come out of their winter slumber.
3. Paste Foods
Paste foods are produced by intercepting the finely milled ingredients prior to them reaching the extruder. Paste foods must be mixed with water to form a firm dough ball that can be offered, a piece at a time, to koi. Paste too is a sinking diet which rapidly stimulates the interest of all the koi in a pond. As soon as a paste is mixed with water, water soluble ingredients leach out into the water, alerting the koi’s acute olfactory (smell) senses that there is food about. The benefits of paste foods is that they are soft and moist and create frenzied feeding activity. However, they require mixing (creating twice their dry weight once mixed) and can cause a little clouding during feeding time (but nothing an adequate filter cannot handle). Due to the issue of leaching caused by the fine nature of the paste flour, there is a risk of koi receiving a deficient diet unless precautions are taken during formulation. Nevertheless, it is great fun to mix and feed koi a paste food.
In summary, having satisfied yourself that you know what to look for in a diet and the nutrition you feel is best for your koi, consideration should also be given to the type of food that you choose to act as a vehicle for feeding that diet to the koi. Pellets (floating and sinking) and paste foods each have their benefits for you and your koi with the final choice of format down to your preferences and requirements.