Shiro Utsuri – from Hero to Zero

The Shiro Utsuri is one of the varieties of koi that I keep. 'Utsuri' is the term applied to a koi that has a single base colour of white (shiro utsuri), or red (hi utsuri), or yellow (ki utsuri). A Shiro Utsuri is white base with black markings. The black markings (sumi) must be deep, solid, and shiny lacquer-black. Sumi actually develops as the koi grows older. Undeveloped sumi may appear grayish instead of solid black on a young koi.  In fact, choosing a shiro utsuri at a young age involves good anticipation of how well the sumi will develop in the next few years. The base colour of white must not exhibit any sign of tint of a different colour, especially yellow.

I also kept Showa which is one of the variety of koi like a Shiro Utsuri but with Red (hi) markings. The Showa has a black body with red and white markings or some even say, a white body with red and black markings. The hi (red) markings on the white body must be solid, deep, and evenly-coloured throughout the entire body. Some has said that a good Shiro Utsuri is like a Showa without the red pattern.

  One of my Showa.

A koi is either a good Shiro Utsuri or a good Showa, not both. Difference is in the red markings.

Over the years of koi keeping, I have the unpleasant experience of faint red markings or spots appearing on some of my Shiro Utsuri. This happens to about 50% of my young Shiros that I bought over the years. They are excellent specimens of Shiro Utsuri when young (less than 2 years old), some of which are from reputed bloodlines and breeders but somewhat develop orange/red spots (not solid red markings like in a Showa!)  a few years later. An excellent Shiro Utsuri has now become a poor example of a Showa or worst, cannot even be classified as a Showa!)

  Two of my Shiros that became “Shirowa”! Hopefully, the red markings on the one on the right will go away as the fish aged.

Fact of the matter is that the Shiro Utsuri as a variety is developed from Showa over many years of selective breeding. So, it is natural that they still carry some Showa genes in them. As the fish aged, the red markings may appear in some of the fish. Some “shiro utsuri” are actually offsprings of Showa parents that happens to be white and black with no red (until later where some Red appears!). I actually heard of  Showa that has its red markings fading away as it grows bigger.

I think it would be better to buy a matured Shiro Utsuri next time, rather than to buy a few of the younger ones. Cost more but it will save the owner some heart-ache a few years down the road.

Filtration System for my Third Pond

My current pond consists of a main Koi pond, a water feature that overflows into the Koi pond and a physically separated garden pond that shares the same filtration system. The drawing below describes the filtration system and I would recommend this as a minimum design to anyone who is thinking of building a new Koi pond. This design overcomes a few problems that I encountered with the earlier filtration systems used for my first two ponds.

The drawing below shows the plan view of the filter.

The first chamber is the gravity pipe chamber or settlement chamber. Water enters the settlement chamber at the bottom from the pond's bottom drains through two 4 inch diameter (100 mm diameter) pipes. Two other lead-in pipes (75 mm diameter) pull water from my water garden pond and also from the bottom drain of my water feature. There is also a small skimmer pipe (75 mm diameter) that removes surface debris from the Koi pond to the filter. The settlement chamber allows for solid waste to settle before going into the filter media.

Each inlet pipe in this chamber is configured with a socket to allow me to push in standpipes to stop water flowing into the filter during filter maintenance. Photo above shows two standpipes in position.

A copper pipe with a tap allows easy refills from the water mains without the need to pull a garden hose. It comes with a float valve (commonly used in cistern) that automatically shuts off the tap water flow when the desired water level is reached. This chamber also contains a 50 mm diameter overflow pipe that leads to a drain.

Filtration Chamber 1 is for mechanical filtration. It contains filter brushes which acts as the mechanical filter. The brushes trap solid wastes and debris like fallen leaves. This can then be removed and hosed down when needed.

Filtration Chamber 2 is for biological filtration. It contains filter mats, placed vertically and supported by plastic grating at the bottom. The mats provide the areas for the bacteria to grow.

Filtration Chamber 3 and 4 is for biological filtration. It contains sacks of crushed cockle shells and coral chips, supported by plastic grating at the bottom of the filter chambers. The shells and coral chips provide the pH buffer needed to control the pH level in the pond. It also provides the areas for the bacteria needed in biological filtration to grow.

The Return Pump Chamber contains two return pumps. The pumps pushed the filtered water back to the Koi pond and water garden. One return pipe goes to my water feature and water garden. The other pushes water out through 3 venturi pipes into my Koi pond. The water feature and venturi pipes provide aeration for the pond. Once water is pushed out from the Return Pump chamber, gravity will draw water from the pond's bottom drains into the first chamber.

Each filter chamber has a bottom drain that leads to the Sludge Chamber through a 40 mm diameter pipe. Ball valves are used to open and close the bottom drains.

A long PVC pipe, with tailored ends as shown, allows the valves to be operated easily from above and makes filter maintenance easy. I can flush the bottom of all my filter chambers, especially the settlement chamber, within a few minutes. This makes the task so easy that I can do this almost daily.

The filter shell is made of thick reinforced concrete, as is the rest of my pond. Pre-casted, one-inch thick concrete slabs are used to construct the filter chambers. Balau wood is used for the removable covers.

Must you change the water in your Koi pond? How often do you do it? How much to change each time?

These are questions often asked by relatives and friends when they see my Koi pond. Whether it is a pond or an aquarium, regular water change is necessary. Actually, partial water changes and it must not be more than 50% of the water at a time. This is because fish (Koi included) does not like sudden changes to their living environment. Furthermore, I have to refill my pond with tap water from the utility company. The tap water contains chlorine to kill germs and it is also a fish killer. I have managed to do up to 40% water change without using dechlorinator which removes the chlorine from the tap water. Any more could be risky for my Koi, a lesson I painfully learnt.

Firstly, why are water changes necessary? Doesn’t the filter remove fish waste and other debris like uneaten fish food, dead insects and plant matters? Yes, a good filter should be able to trap solid debris through mechanical filtration and allows you to remove them easily during regular filter maintenance. The filtration system should remove dissolved fish waste like ammonia by converting them to nitrite, and then from nitrite to nitrate. This is done through bacteria action in the biological filter. Ammonia and nitrite are harmful to fish and must be removed as soon as possible. Hence the need for a well designed filtration system. Although nitrate is relatively harmless to fish, excessive nitrate when allowed to build up in the pond can still harm the fish and also cause problem of excessive algae growth. Water plants remove nitrates. Although I have included a water garden in my pond design, I doubt the plants can remove the nitrates at a sufficient rate compared to the amount of food consumed by the Koi each day (= waste produced). Therefore, even with an excellent filtration system, partial water changes is necessary to remove the nitrates. I notice my Koi becoming more active and lively after a partial water change.

Next, how often do you perform the water change? If you have a large pond, intervals between water changes can be longer. I do it at least once a week although my pond can withstand a longer period without any water change. This is because my filter design (with the bottom drains in each filter chamber leading to a sludge chamber holding a drain pump) makes this an easy task. While making the partial water change, I would flush the bottom drain of each chamber in my filtration system. It takes only a few minutes and about half a cubic meter of water is removed each time.

To reduce the amount of tap water needed for the refill, I would try to do my partial water changes when rain is imminent. I do get a lot of rainfall in Singapore during the wet season.

On a quarterly basis, I would do my filter maintenance and flush one of the filter chambers and at the same time do a larger volume of water change.

But not more than 50% at a time!