Feeding and Growing Koi – The breeders perspective

Over the winter we grow our tosai in heated buildings which allows them to experience what are effectively summer conditions all year round. Having said that, this year, as usual, they weren’t harvested until October and once transferred to the tosai house, they weren’t heated immediately, so they have had a little bit of a winter.

Koi produce the most growth hormones within the first three years of life, so, like us, many breeders tend to make the most of that by providing an environment in which the Koi can keep growing. Some Koi, even from the same spawning, will grow faster than others and so most breeders will choose the best quality and fastest growing Koi to grow on over the winter months. Of course, heating water is pretty expensive and some breeders just don’t have the facilities or money to do this, but those that do, tend to make the most of them.

Every breeder who has a heated system will bring their best tosai in over the winter and grow them on, just like we do. Few breeders have the facilities do this with older fish as this is a big investment for what is likely to be a comparatively small volume of Koi – only the very best few are kept on the farm once they have reached Nisai. I do know however that at least one of the most successful Koi farms in Japan does exactly this.

The type of food fed by breeders will vary from farm to farm and will depend on a variety of things but which food each breeder chooses will be dictated by the cost and the quality of the ingredients. One way of making a food cheaper is by including a higher quantity of wheatgerm which also has the affect of bulking the fish out – a bit like eating a lot of bread and cakes does to people!

Each breeder will have their own preference for feeding and it will be based on their budget and the environment their Koi are raised in. Some of the best breeders choose to always feed colour enhancing food to Koi that they are growing on and there is logic to this if you consider that in a concrete pond the Koi are not getting the benefit of the natural colour enhancing algae that they would get in a mud pond during the summer.

We use a food produced in Holland and we chose it because we believed it to be a good quality food developed after extensive research and trials against other leading brands of Koi food. Mark visited their research and development site and also their production facility and had the opportunity to chat with some of the staff. Some of the findings and results of their comparative studies were very interesting. Personally, I have researched the ingredients myself to discover what they are and what benefits they give to the Koi. These are the reasons why we use the type of food that we do but there are several good Koi foods on the market and I would recommend you do as much research as possible when choosing which food is best suited to your Koi and your situation.

We use two types of food – one a good quality but basic carp diet with a protein content of 45%, and the other a specially formulated Koi diet which includes immune-stimulants, aids to better digestion and colour enhancers – it also happens to have a high protein content, which at 51% is a little over the top but which was set at this level because it was found to be the level of protein that is consumed by Koi in their natural environment. Having a high protein content isn’t in itself harmful to the Koi as they will simply absorb what they need and will then excrete the rest. It could be considered a waste of money although it wasn’t the high protein level that led us choose this food, it was the combination of ingredients as a whole.

As a breeder, we are in a unique position to do our own trials and that is exactly what we have been doing. Last winter, in our Nisai house, which was heated to around 23 degrees C, we fed two tanks of fish with the expensive all inclusive food and the other with the basic carp diet. Most, but not all of our Go-sanke were in the tanks which were fed the food which included the colour enhancer and most, but not all, of our Shiro Utsuri were in the tank that were fed the basic carp diet.

I must admit to some trepidation to doing this as I had heard that feeding colour enhancing food over a long period of time might lead to hi spots or cause the Shiroji to take on a yellow tinge. We are never ones to walk away from a challenge though and after a whole winter of sticking to this regime, we found that in the tanks which were fed the more expensive food, our Go-sanke still had persil white skin, their colours were vibrant, body shapes good and they were in the best of health. We had three Shiro Utsuri on this food and two of them had slightly more creamy than white skin but the other had excellent white. The Koi fed the standard diet had just as good growth rates and the colours were still vibrant. The shiroji on all these fish was excellent and the colours on the Go-sanke didn’t fade at all. (I must point out that in our own indoor growing on systems we have no natural light and so we have considered what effect that this might have on any Koi growing in them, for example it might lead to colours fading in particular.)

This year we are feeding only the basic carp diet to all our fish on the farm and the fish in our Nisai house are not heated – this trial is still underway but the results are looking good. Incidentally, we have never fed anything but the basic diet to the Koi in our sales tanks or mud ponds as we have never seen the need to do feed anything else – the fish grow well, don’t get “fat” and are healthy.

We found that the cheaper food that we feed has a higher percentage of vegetable protein than the more expensive one and so the fish produce more waste which means a greater potential for build up of organic material and therefore bacteria in the system.

Mark has designed systems that are easy to maintain and makes the time to maintain them properly, so we don’t suffer with bacterial or water quality problems. Some Koi keepers however would rather spend their money on a more expensive food with a higher fish meal content, such as the higher protein food that we have also used, that produces less waste and leaves the system generally cleaner and easier to maintain. I’m not going to tell you which food you should be using, I’m just highlighting some of the aspects that you might like to consider when choosing a food for your own Koi and suggest you do your own research and if you’re not totally happy with the results you are getting with the food that you are currently using, try something else!

We have been approached several times by Koi food suppliers to persuade us to use their food so that they can use us to endorse their product. We always thoroughly research the ingredients and question the research behind the foods being offered though and we have yet to find anyone that can convince us that they have a better product than the one we are already using.

Lisa