Project Mud Pond

You may remember an old video series called The Yamakoshi Trilogy, which provided a fascinating insight into the 3 main seasons of koi production in Japan. Back in 2001 I would watch these tapes constantly, one after the other, drifting away to my own little world. These videos were the main source of inspiration for a lot of my future dreams, one of which was to have my own mud pond in Japan.

You may ask yourself what the fascination is with mud ponds, because ultimately, they are just big holes in the ground, full of water – and you can only see the Koi when they are right on the surface. Somehow though, there is an aura of mystique around mud ponds; on top of that, they can transform Koi after spending the summer in one.

It is very common practice these days for people to buy individual pieces and leave them with the breeder for a year or two. This is known as ‘azukari’, which literally means ‘to care for’. This completely leaves the fish in the hands of the breeder, however, and you do not get any input as to how the fish is cared for, or which pond it goes to. I wanted to take the whole process one step further and have the mud pond at my disposal for the koi that I selected.

As I said previously, the transformation that can occur over a 5 to 6-month period in a mud pond can be sensational, but there is a great deal of risk involved. Mud ponds can be very volatile, as aside from minimal interference from the breeder, they are very much left to nature. Risk from predators and natural disasters are two of the biggest concerns; the mountains are full of animals hunting for their next meal and natural disasters such as earthquakes and typhoons are very common in the country. Even the extreme heat can cause problems sometimes, especially when coupled with low amounts of rain; this causes water levels to drop which results in breeders having to feed less.

So, with all this potential risk why do we as koi keepers still remain so fascinated with them? I think the answer is simple when it all comes together – and it works; the results can be incredible. First of all is the potential for growth;  mud ponds are exceptional for gaining mass body volume in a relatively short space of time. The vast amount of space, low stocking levels and ample natural food resources (high protein, high fat treats like snails) help stack the body on. The muddy waters can also work wonders for the skin quality, particularly the lustre, which can easily be lost through poor water conditions in concrete ponds. Once you have seen a few harvests and followed some Koi from start to finish, the desire to have your own piece of the action begins to burn away.

My own experiences with Azukari so far have been good; being able to select the right Koi is important, as not all fish have the quality to improve in this kind of environment. A Koi with somewhat average qualities can be helped along when kept in an indoor pond with plenty of natural light and relatively steady growth, it allows the pigmentation to develop and keep what could be relatively low-class colour limping along. In a mud pond you can’t get away with this, UV penetration only breaks the surface of the water and the fast-paced growth will very quickly consume low quality pigmentation – to the extent that what went in as a Showa becomes a Shiro Utsuri in no time at all.

I’m always up for a challenge and I wanted to put my skills to the test and select a number of very small (15-19cm) tosai and have my own mud pond in which to grow them over the summer. After a discussion with the guys at NND (Nishikigoi Niigata Direct), I got them to agree to give me the chance to select from a pond of small Tategoi which would be the grade I required for this project. Furthermore, I managed to secure a mud pond in the mountains of Yomogihira to house them over the summer. The pond would be cared for by Makoto Tanaka (Marusho), but I was able to work on the feeding regime which I was keen to do.

The selection was done back in February and for me it was like being a kid in a candy shop being able to select through such a pond of Koi. Varieties available were Kohaku, Sanke, Showa, Ginrin Showa and Kikusui. After spending a couple of hours going through the pond I selected 50pcs, the maximum capacity for my mud pond. Each fish was then measured and photographed before being moved to their new home until they would be released to the mud pond in June.

Having selected the Koi at around 15-17cm on average, I am expecting to harvest them at around 35-40cm. A growth rate of around 20cm per fish is more than achievable with smaller tosai over the 5month growing period. What this extreme growth also does is completely change how most of the Koi will look. Small Showa are the best example I can give here; as you will see from some of the pictures it doesn’t look like they have much shiroji (white skin) and have too much underlying sumi. This is not the case because this appearance is caused by the fact that the white skin is very translucent at this age – and with the growth spurt will come an increase in skin thickness, pattern movement and more body mass. So, the overall look of the pattern will change and the areas where it looked, as if it would all be sumi become areas of shiroji. Ultimately you can’t be too critical with them at this stage and really just assess the qualities that are in front of you; after the harvest when the Koi are nisai it’s time to re-assess with new criteria.

In June while I was in Japan again, I had arranged to go and release the Koi into the mud pond and this, on its own, is a great experience. This is the last chance to see them up close until the harvest. Having packed all of the Koi onto the truck it was a windy drive up the mountains, then a slightly scarier trek down a precarious looking road to the mud pond. All of the fish were moved to the pond and acclimatised before slowly being freed to their new home for the summer. Then it was just a case of putting the predator netting around the perimeter of the pond and letting them adjust to their new environment. It would be another week until the automatic feeder was set up, as both the Koi and pond need to adjust before cranking up the feeding. Too much too soon and the Koi can very quickly lose conditions, which is not ideal when they are in a mud pond.

Now I anxiously await the up and coming harvest of the pond to see how my selection turned out. All 50pcs were photographed on the day I bought them, with each due to be photographed after the harvest. I can’t wait to share some side by side comparison shots and my thoughts on the results.


  1. Brilliant article and the koi look very very nice can’t wait for the update and too see the results

  2. Great read Ricky I too still watch the Yamakoshi Trilogy and sometimes another one called Spring Time in Niigata with some young kid picking koi😉 have you watched it

Leave a Reply

%d bloggers like this: