With the water quality improving after the installation of Vortex Filter, 2 new Chagois were added to my pond. Both at about 10″ length purchased at RM 300 a piece. With my 5ft deep pond, the Chagois will have no problem growing to a length of 70cm in 1.5 years.

Chagois will be netted from the pond and measure every two months to monitor their grow.

Sand Filter is commonly used for swimming pool for keeping the pool water clean and clear. There are some koi pond owners use Sand Filter in the final stage of filtration process to polish their pond water. In my ten years of keeping koi, I have also installed a sand filter for my pond system but I have merely ran it for six months. The sand filter and the centrifugal pump that is required to feed the sand filter has since idled.

I must agree that Sand Filter is excellent in polishing the pond water and the end result is a crystal clear pond water which allow me to see the base of my 5ft deep pond easily. The sand filter that I used was filled with sand and some zeolite and to push the water through the filter, a 1HP centrifugal pump is used to pump the water from the last stage of filtration and the water return to the pond after the polishing process.

1 Horse Power or 750watt equal to the power consumption of 5 Tsurumi pump and that is a lot. The use of Sand Filter immediately pump up my electricity bill substantially and that is one main reason that discourage me from using it further.

After using the Sand Fitler for one day, you will notice that the presure built up in the piping system leading to the sand filter increased substantially and there is always a need to backwash the filter once a day to clear the clog and reduce pumping presure. Having to do that is quite troublesome and in the process of backwashing, you will lost quite a lot of pond water as well.

Overall, the Sand Filter is easy to install. The PVC pipe require for the installation are that of greater thickness that are able to withstand high operating presure of the sand filter.

After using the sand filter for a few months, you will notice that the backwash action will not reduce operating pressure very much and that indicate that the sand has clog up quite alot and there is a need to open up the sand filter chamber to clean the sand inside.

A filter that require too much maintenance is not fun in koi keeping hobby and finally I gave up the use of sand filter after only six months of use.

While Trickle Tower has been widely used for Koi Pond, many have also included a trickle tower in large aquarium where the water is overflow through a trickle tower to a bio filter located below the aquarium. I have however installed a simple Trickle Tower for my small aquarium and it is equally as effective as it cousin that we used for koi pond. The rule is again to have the water trickle slowly. Some of the pictures are as below:-

Previous post on Trickle Tower for Koi Pond :-
https://www.khoo.name.my/2005/11/21/removal-of-nitrate-from-pond-water-system-koi-pond/

Any bio filter in a koi pond system that is matured after been colonized by nitrifying bacteria will sure produce a lot of nitrate in the pond water system as a result of the following process:-

Fish Waste (Ammonia) => Nitrite => Nitrate

While Nitrite and Ammonia are very toxic to fishes, Koi are able to tolerate Nitrate to a certain extend but nevertheless, it is still very important to remove Nitrate from the Koi Pond system to ensure overall health of Koi Fish and no green water.

Generally, Nitrate level in the Koi Pond can be reduced by the following methods:-

1) Regular water change
2) Installing vegetable filter
3) Installing Trickle Filter

Of all the three methods mentioned above, the easiest way to remove Nitrate is by regular water change. Rule of thumb is to change at least 20 ~ 30% of pond water weekly. For small koi pond, this method can be implemented effectively and economically. For larger koi pond, this method will turn out to be very costly to pond owner as substantial volume of water replacement is required.

The 2nd method is to install a vegetable filter. Pond water that passed through the bio filter can be lead to a series of long water way planted with water plant. The purpose of the water plant is to absorb nitrate from pond water as fertilizer. This method require a lot of space for the construction of water way and the plant need to be maintained regularly as you will see that the plant will grow very fast with plenty of nitrate to absorb. To save space, I once planted a yam tree in the final stage of my filter system and mind you, the yam tree grow extremely fast and a lot of trimming is needed at very close interval.

To me, the best , method is to install a Trickle Tower as it require very little maintenance and yet it is extremely effective. A simple diagram showing the trickle tower is as below:-

Drawing taken from Koi Kichi, a popular book on Koi by Mr. Peter Waddington

I have constructed my trickle tower using plastic tray and with a lot of small holes drilled at the base of the tray so that water can drip down to the next tray.

Four trays are stacked together in the vertical position to form the trickle tower. Water from the last stage of filtration are pumped into the top of the tower at very slow flow rate so that water can trickle slowly through the tower. The water that are collected at the bottom tray are then diverted back to the first stage of filtration.

We have tested the trickle tower with different flow rate and found that slow flow rate tend to be much more effective and efficient.