Wooden Decking for Koi Pond Filter

The wooden decking that covers the filter of my third pond is rotting! And they are only about 3 years old. I am not sure why this happens. I think it could be that the wood is not properly treated and painted. Also the prolonged rainy weather over the last year could have played a role. Another factor could be that the wood used is not Balau wood as specified.

The recommended wood material for making the Koi pond decking or any outdoor furniture in South East Asia would be the Chengal or the Balau wood. Chengal wood is better but more expensive, so I have agreed with my contractor to use Balau wood instead.

The wooden decking in my previous pond was much more durable. No signs of rotting even after two to three years in the sun and rain.  The material used for that pond decking was Chengal wood, AND the wood planks was painted with Hickson paint before and after installation AND held together using stainless steel nails.

I am going to make sure that my new filter decking is done properly this time….if and when I replace it in the future.

Koi pond at Rasa Sentosa, Singapore

This is first week of the school holidays in Singapore. After returning from Manila to Singapore, my family took a short weekend break in Sentosa island, a place popular with tourist and locals. We stayed at the Rasa Sentosa Resort, which had undergone some renovations recently. But what did not changed was the beautiful Koi pond at level 1, which is just outside the lift lobby leading to the beach and swimming pools.  There is a placard next to the pond explaining the following:

“Nishikigoi or Koi is considered auspicious, representing long life and prosperity. Contrary to common belief, koi are not indigenous to Japan but originate from Eastern Asia and China, and are descendates of the black common carp. The fascinating and colourful koi varieties that we admire today are the result of almost two centuries of selective breeding and their popularity is fast growing in many parts of the world”.

The Koi pond is massive and the layout and overall pond design is beautiful. I like the stepped design, with water cascading down from a higher pond level to the lower level where the Koi are found.

This is an example of an excellent pond with informal layout, with beautiful landscaping and rocks around the pond. Pandans, bird nest and boston ferns, monstera deliciosa and other tropical plants and tall trees around the perimeter of the pond give it a natural and tropical jungle feel.  NICE.

This part of the pond recreates the effect of a stream, with water cascading down into the main pond.

Koi Pond at New World Hotel, Manila (Pt 2)

 

I will be checking out from this hotel later today to catch a flight home. After my breakfast, I visited the koi pond again. There is a person cleaning the pond this morning. He was vacuuming the bottom of the shallow pond using a pool vac. This highlights the importance of having a good pond design. Features like bottom drains and venturi pipes strategically placed to create a water flow around the pond and moving detritus from the bottom drain will reduce or eliminate the need for such back breaking maintenance work.  Also, for a deep pond, walking around the pond to vacuum the bottom is impractical, if not impossible.

Another feature lacking in this hotel’s Koi pond is a surface skimmer. The surface skimmer serves to removes oil, scum, floating leaves, dead insects from the water surface Without a skimmer, the pond keeper may have to sieve such dirt out by hand.

This pond also houses several large catfishes called the pleco. The pleco feeds on algae and is a bottom feeder. They are also known to eat floating Koi pellets by swimming inverted at the surface. Some people believes the pleco helps to keeps the pond clean. I tends to disagree. What goes in, must comes out. While they clear the pond from algae or other plant material, they are also producers of waste.

Koi Pond Pump Selection Tips

The submersible pumps are the heart of the Koi pond.

Key specifications or rating for the pumps:

• Voltage = Voltage required in Volts (V).
• Current Drawn = Amount of current drawn, rated in Amperes (A)
• Power consumption = amount of power consumed rated in Watts (W)
• Flow Rate or maximum capacity = volume of water moved over time. Typically in cubic meters per min (m3/min) or litre per min.
• Maximum Head = maximum height of water that the pump can push water through. For example, the vertical height between the outlet of pump (e.g. top of waterfall) to the inlet to the pump (e.g. at the bottom of the pond or filter. The flow rate is inversely proportion to the head of water to be pushed.

The flow rate and number of pumps needed depends on many factors. There are many articles written on this subject and the rule of thumb is this: “Half the pond’s capacity (volume) needs to flow through the biological filter every hour”. So, do the calculations to determine the number of pumps and ratings of the pumps needed based on the capacity of the pond.

Depending on size of the pond, try to have a few small pumps than a single large one for redundancy in case one pump fail.  In addition, having a number of smaller pumps allows you to adjust the flow rate up or down by turning one or more pumps on or off. Connect them to separate power sources (with circuit breakers for safety) to create higher availability and redundancy.  As the electrical power cable for the pumps is usually about a few meters in length only, locate the power supply points as closed to the pump chamber of your filter as possible.

Have a spare pump in your house, especially if buying one requires a lead time longer than a few hours.

Other features to consider would be the auto cut-off when there is no water (useful for drain chamber).

For me, the pumps must be long lasting and be power efficient.   I am currently using 2 units of Tsurumi pumps (Model 40PU2.15S). They has been running almost non-stop for over 2 years now and consume a relatively low power of 150W each. In addition, I have another pump with auto-cutoff feature in my drain chamber; the drain pump is only used during pond maintenance.

When installing the pumps, devise a way for them to be removed without having to drain the pond or filter. Have a pipe coupling that allows the pump and attached outlet pipe to be decoupled at the top of the pond or filter. The whole pump, with the attached outlet pipe can then be lifted out for replacement.

Koi Pond Bottom Drains

A key feature of a well-designed Koi pond are drain pipe(s), also known as the Bottom drain(s),  linking the bottom of the pond to the inlet of the filter system.   In my current 13-ton pond, water enters the filter 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. See my earlier post on filter design. 

Location of bottom drains.

The bottom drains should be near the geometric center(s) of the pond, and evenly spaced out if you have more than one bottom drains. A good pond design will be to slope the bottom of pond towards the bottom drains. This allows any physical dirt at the bottom of the pond to be pulled  towards the drains by gravity.

The bottom drains should draw pond water into the filter. Each bottom drain should have its own pipe into the filter chamber. It does not make sense to have 2 or more bottom drains daisy-chained via a single or shared pipe (water will only flow in through the pipe with the least resistance and the other drains will be mostly ineffective). Typical size of pipe is with 75 to 100 mm diameter.

Importance of having a good drain cover.

Drain covers can ranged from simple DYI covers to commercially-built drain covers. My current pond uses a simple mesh, force-fitted onto the top of the drain.

A Koi should not easily dislodge the cover. I have lost a few Koi in my first 2 ponds after the cover was dislodged and a Koi found their way into the filter.

Using Pineapple to Run-In a Concrete Pond

This is an email i received recently from a blog visitor.

Hi Jeff,

I have just completed my koi pond. My contractor told me to "put in pineapple skins" into the koi pond for a few days to "clean the pond" and rid it of toxins from cement etc.  before cycling it and putting fishes.

Is this the right way to do it ?

I guess this could be a good practice to follow for concrete ponds. Since pineapple is acidic and should reacts and neutralise the cement (alkaline) which may leach into the water over time if there is no epoxy sealant used to coat the surface of the concrete pond.  In fact, on similar advice from my contractor who built my first 2 ponds, I did put in pineapple skins into my pond water for a week or more before cleaning the pond and doing a 100% water change. I bought half a dozen pineapples and used the skins and core while we ate the flesh. Pineapples are relatively cheap in South East Asia, but I guess other mild acids can probably do the job too.

For my third pond, I told my contractor to coat my concrete pond with epoxy sealant. That will prevent cement leaching alkaline into the water. Choose black colour sealant paint. Your Koi will stand out beautifully against the black background.  In any case, my filter compartments are not coated, so I may actually need to do the “pineapples treatment” but I did not.  Maybe that was the reason I lost some of my Koi in my new pond initially. But that could be due to other causes e.g. immature biological filter or excessive water changes. Steps to introduce fish to a new pond is a topic for my blog for another day.

So, to be on the safe side, just do the “pineapples treatment” and enjoy your pineapples.

Koi Pond Design Checklist

The following provides a quick summary or overview of the considerations when you are planning or designing your first or subsequent Koi pond. Each point will be further elaborated in future posts if not already shared or discussed in previous posts on this blog.

* Location of your pond

This is the first and most important consideration since it will drive the design of the rest of the pond. Typically, this will be considered together with the size, shape and style of the pond. There may be constraints such as existing layout of your house, environment and other factors.  Your personal reasons for having a Koi pond will be key considerations. These could include:

• A feature or place in the house for relaxation. In this case, locate the pond close to your house where you can view your Koi easily.
• To keep Koi as a hobby  
• To fit or complement the overall building or house design and to add to its aesthetics.
• Geomancy or Feng Shui, i.e. to bring good luck to you and your family. Consult a Feng Shui Master or geomancer if this is a key reason.
• To also keep aquatic plants or water gardening. For these, the pond must be located where it will receive at least 4 hours of direct sunlight per day. More if you want your water lilies to flower regularly. 
• As a garden feature.

Check out my previous posts describing the layout and location for my first, second and third ponds.

* Style or shape of your pond

A formal pond is one with standard geometric shape (rectangle, square, circle or ellipse).  A formal pond will look best in a formal setting such as against a tiled up patio, against a house wall or at the centre of a large open lawn. An informal pond is one with a shape that appears to naturally form. Common shape would be kidney shape or any irregular shape that can fit into a garden setting. Formal or informal is a matter of personal preferences. My first and second ponds are informal ponds, while my third pond is a formal pond.

* Size and depth, volume

You will have to consider the Koi environment needs when deciding the size, depth and volume of the pond.

* Pond Construction Material

There are typically 3 options - concrete pond or using a pond liner or use a pre-formed bowl. For large ponds in South-East Asia, most Koi ponds are built using reinforced concrete. Smaller ponds will use a pre-formed fibreglass or plastic bowl or shell.

For concrete ponds, it would be essential to coat the surface with special epoxy sealant paint.

* Filter design or filtration system

The filtration system is the most important element of a Koi pond. Key considerations would be

• Build (custom designed in-ground filter) or Buy (commercially designed external filtration systems)
• Size of the filter, number of compartments, media type
• Location of your filter
• Bottom drains

The water quality would depend heavily on the design of filtration system and it will determine the health of your Koi, and overall beauty of the Koi pond and its surroundings. A good filter system will also make filter maintenance and pond maintenance easy.

* Pumps

This is often planned and selected together with the filtration system. If the filter is the “kidney” of the pond, the pumps are its heart. Selection of the right pumps to use is just as important as the filter design as it will affect the water flow rate, effectiveness of the filter system and workings of water features, especially waterfall or fountain.

* Aeration and water features

Koi needs oxygen and so does the bacteria in the biological filter. Besides the natural absorption that occurs at the pond water surface, any ways to agitate the water artificially will increase the oxygen absorption by the pond water. Consider having a waterfall for aesthetic reason, as well as for pond aeration.  Waterfalls are ideal for informal ponds. Plants and rocks formation can create a beautiful natural setting. For formal ponds, consider having a fountain. Such water features also create the soothing sounds of gurgling water in my home.

In any case, do consider using venturi pipes.

* Overflow pipe

Don’t forget this small but essential feature. It allows excess water, e.g. during heavy rain, to overflow into a drain.

* Surface skimmer

Every pond ought to have a way to remove floating debris from the water surface. Dust, oil, protein scum, and small floating debris (insects, dead leaves) can be removed with a surface skimmer device.

* Bottom drains

This is important feature for your pond and in-ground filter system for easy maintenance.

* Water plants

Whether to include water plants in your Koi pond or not would depends on the style and shape of your pond. The overall design and layout of your pond will need to be planned carefully, together with the types and species of water plants that are suitable for Koi pond. Check out the various posts I have on this topic.

* Edging

The edging of your pond could serve a few purposes:

• Prevent surface water runoff during rain from entering your pond.
• aesthetics
• safety barrier
• platform for feeding and netting or capturing your Koi

If your pond is an informal garden pond, the edging is important as you would want it to blend with the rest of the garden or setting.

* Platform or place for Koi feeding and capturing or netting of your Koi

It is good to consider where you would stand to view and/or feed or catch your Koi safely. Avoid protrusions (e.g. venturi pipe, overflow pipe or skimmer) or even water plants near the place where you intend to feed your Koi as they may feed in frenzy and knock themselves against such protrusions.

* Lightings

One of the considerations when designing your pond is Pond Lighting. Should you include underwater lights, type of lights to use, locations of light points, is it good for the Koi? What about safety, since electricity and water should not mix? Check out what I did for my 3 ponds here.

* UV Light filter

UV light filter may be useful to as a means to control bacteria or parasites, kill germs and sterilise the pond water.

* Water supply

Easy source of water supply must be provided near your pond for water changes and replacement of water lost through evaporation. Have a tap or faucet located next to the pond. Better still; build a water inlet pipe directly into the pond.

* Power source for pumps (and separate one for lightings)

Best is to have multiple power sources, with individual circuit breakers and isolators for each pump that you have. That way, a single pump failure would not knock out all the pumps and stop water circulation and aeration.

* Choosing your Contractor or Build your own

In South East Asia, most Koi ponds are concrete ponds. For a concrete pond, it is best to engage a professional or experienced Koi pond builder.

Pond building is an art and it is good to engage a Koi pond specialist rather than rely on building contractors who may be experienced with building water features or swimming pools but not a Koi pond. A Koi pond has special requirements on depth, filter design and size, pumps to use, locations of venturi pipes and bottom drains, aeration, shape, even special sealant paint for the sides of the pond (not tiles) ....just to name a few. It is best is to design and build it right the first time.

Hope you find this list useful and a good starting point for you to design your pond or discuss your needs or specifications with a professional pond builder.

Water inlet pipe for your pond

Ideally if you are refilling your pond using tap water, the water should be de-chlorinated before adding the water to your pond as chlorine harms fish. For me, I would add tap water directly into the pond when doing partial water changes of less than 20% of the pond volume or just topping up water lost through evaporation.

Having a water inlet that leads directly into the pond would save you the trouble of pulling a long garden hose to your pond. So, consider including this feature in your pond design.

 

Ideally, the pipe should be terminated with a float valve (commonly used in cistern) that automatically shuts off the tap water flow when the desired water level is reached. For my second and third pond, the inlet pipe is located in the first chamber of my in-ground filter as shown above.

I have a bad experience in my first pond where I do not have such a feature installed and I was using a garden hose. Topping up the water in a large pond could take longer than an hour and it is common to leave the water running unattended …and horrors, completely forgotten. This leads to waste of water as excess water goes down the drain through the pond’s overflow pipe. In the worst case, too much chlorinated tap water entering the pond could result in fish harm or death from the excess chlorine in the water.

Pond Builder – Who should I engage to build my Koi pond?

Over the past few months, I have received several similar queries from my blog visitors who asked me for recommendations on pond building contractors.

In South East Asia, most Koi ponds are concrete ponds. For a concrete pond, it is best to engage a professional or experienced Koi pond builder.

Pond building is an art and it is good to engage a koi pond specialist rather than rely on building contractor who may be experienced with building water features or swimming pool but not a Koi pond. Koi pond has special requirements on depth, filter design and size, pumps to use, location of venturi pipes and bottom drains, aeration, shape, even special black paint for the sides of the pond (not tiles) ....just to name a few.

Also, once a concrete pond is built, correction is difficult to make without risk of leaks. It is good for the contractor to show you some reference sites.

My first two ponds were built by a pond-contractor that was a subcontractor to a landscaping contractor. Being new, I have to depend on a contractor who can show me references of past projects done. 

My third pond was built by a contractor who did also did the alternation and additions (A&A) works for my house.  Although I was happy with my earlier pond contractor, I choose this new contractor for my third pond because the pond is “integrated” into my building design and my builder happens to be also in the Koi pond building business. You can compared the filter designs for the 3 ponds and see that the designs are very similar but the filter for 3^rd pond is probably the best of them all since I do not have the space constraint that I faced with my first 2 ponds. I reviewed the pond and filter design for my third pond based on my experienced with my first 2 ponds and proposed design by the contractor is very close to what I had in mind.

At the end, you still need to engaged a contractor you can trust. Get them to show you the proposed design and it should have the features of a good filter and attractive pond layout to suit your personal needs.

Lighting for Koi pond

One of the considerations when designing your pond is Pond Lighting: Should you include underwater lights, type of lights to use, locations of light points, is it good for the Koi? What about safety, since electricity and water should not mix?

I did not use any under-water lightings for my first 2 ponds. For my first pond, I did not think of lighting up the pond before it was built. When I tried shining a spotlight on my first pond, the occupants got a fright of their life. Some of my Koi though they were flying fish and 2 landed out of the pond. Fortunately, I have quite dense plantings around the pond and they were not badly injured.

This stopped me from shining any more light on them. It also stopped me from including underwater lighting or spot lights for my second pond.

Later I found out that using less powerful halogen lights and/or underwater lights could be done without panicking the Koi.  On advice from my pond builder, halogens lights were fitted just above the water for my third pond.

By positioning the lights just above the water, it created a very nice “dancing light” effect when the lights are reflected off the water surface and onto a wall. In addition, overhead halogen spot lights are used to light up key pond features, e.g. water plants and water features to give a very nice resort feel to the home.

The halogen lights (12V, 50W) come with step-down transformers, so there is no danger of high voltage electricity coming into contact with water.  Water-resistance casing are used to house these transformers and also the 230V AC electricity source.

However, there was one problem which I encountered. Since my lights are mounted just above the water surface, some even half-submerged and/or positioned outdoors, my builder recommended halogen lights designed for underwater use. The bulbs burned out within a few months due to overheating. So, I have to change the type of lights or use them fully submerged in the pond. I choose the latter for now.

 

For more information on pond lightings or to buy online, click here.

Submersible Pumps for Koi ponds

The pump is a key component in any Koi pond. In my first pond, I was using the following pumps, with the following ratings and specifications.

Nova 600, 800 W, 220V, 3.4 A, 16 cubic m/hr. Power consumption per month = 584 KWH

Nova 200, 350 W, 220V, 1.5 A, 12 cubic m/hr. Power consumption per month = 250 KWH.

Although my filter was fitted with 2 pumps, one with return to the waterfall and the other returning through the venturi pumps, I typically only turned on only one pump as it was enough to maintain a good circulation and provided enough aeration for my 7 cubic meter pond. Another Nova 200 serves as a drain pump.

For my second pond, I continued to use the Nova pumps but only using the Nova 200 as it was more efficient. Most of the time, two pumps are in operation for my 13 cubic meter pond. Another Nova 200, with an automatic cut-off feature, serves as a drain pump.  The automatic cut-off feature stops the pump once the chamber is empty of water.

The Nova pumps typically lasted about between 2 to 3 years, with almost non-stop operation. When the pump fails, my circuit breaker will trip.  Hence I suspect the failure is caused by a breach of the seal or gasket with moisture getting into the electrical motor and/or there is earth leakage current.

In my current pond, I am using the Tsurumi pumps with the following ratings and specifications. 

Tsurumi Model 40PUS1.5S, 150W, 220V, 1.6A, 11.4 cubic m/hr.

These Tsurumi pumps give better energy efficiency. Two pumps are running non-stop with one return through 3 venturi pipes and one return to a water feature and one venturi pipe. A third pump with auto cut-off feature serves as a drain pump for the waste chamber .  They are now about 2 years old, running since Jan 2008. I also have a spare pump in my house for rapid replacement should any of the above fails.

UV light filter for algae control in koi pond

I received a question recently from one of the visitors to my blog asking if I was using UV light filter since I did not write anything about it. He was wondering if UV light filter is good for preventing algae bloom.

I did not use UV filter for my first 2 ponds. A UV filter was installed in my current pond’s filter system in Jan 2008 when it was built by my pond builder. The water from the return pump was passed through it before being released back to the pond. I cannot really tell if it was effective or not. Right now, I am not sure if the bulb is still working since I can’t see the light. Any way to check without opening up the filter?

I have no problems with algae bloom in all my 3 ponds, with or without UV light filter. I don’t think a UV light filter is necessary as a means to control algae. Algae is caused by high nitrate levels in the pond. Once I feel the nitrate level is high (slight increase in algae seen or water tint) and confirmed through water testing, I would do partial water change to reduce the nitrate levels. Better to control nitrate (the cause) than algae (the effect).

Having said that, I think a UV light filter may be useful to as a means to control bacteria or parasites, kill germs and sterilised the pond water.

For more information on UV light filter or to buy UV light filter and accessories online, click here - ( US Customer, UK Customer)

Simple Surface Skimmer for Koi pond

Every pond ought to have a way to remove floating debris from the water surface. Dust, oil, protein scum, and small floating debris (insects, dead leaves) can be removed with a surface skimmer device.

The following picture shows the simple surface skimmer I used for my 3 ponds. I am using a gravity-fed filtration system. This skimmer pipe leads to the first chamber of my biological filter system. Alternatively, you may want to link this pipe to the second chamber to provide faster water flow since the water level in the second chamber is slightly lower than the first (due to gravity effects and water flow resistance between the first and second chamber).

 

The construction is simple. A 75 mm or 4 inch diameter PVC pipe that protrudes slightly above the water surface. Slots are cut to allow surface water to enter the pipe.  In my case, the slots are a little too big and my floating koi pellets are entering the skimmer through them. Hence I need to add a netting to solve this problem. Don’t make the same mistake. Cut narrower slots and have more of them around the pipe.

The skimmer is best located at a corner of the pond, near your filter. It would be best if you are also using venturi pipes for aeration and  have position your venturi pipes in such a way as to have water circulation around your pond.

Koi Pond or a Water Garden, Why Not Have Both?

Most Koi keepers will tell you that Koi and water plants do not go well together. There is some truth in it as Koi eats plants. Some serious Koi lovers will not include any plants in their Koi pond. They would keep their pond layout simple. Their main or only focus is on their expensive, show-grade Koi and they would not want sunken plant pots that the Koi may bump into or fertilisers and rotting plant waste that may contaminate the pond water. Although water plants do help remove nitrates, increase oxygenation and provide shade, the serious Koi lovers’ ponds will have other means to take care of these.

However, most pond keepers, including myself, would like to have some greenery in their Koi ponds so as to have a pond that looks natural and able to blend with the overall garden. The best compromise is to include a separate water garden that contains other fishes and aquatic plants, that is physically separated from the main Koi pond that contains only Koi, but sharing the same filtration system to reduce cost. It is important to decide this as you design your pond and plan the layout. A water garden is usually shallower than the Koi pond which is ideally more than 4 feet (1.2 meters) in depth. Another solution is to include a narrow and shallow shelf (of about 1 to 2 feet deep) at the edge of the Koi pond where water plants may be grown. In any case, the selection of suitable plants for your Koi pond is important as Koi eats plants.

Water plants can be broadly classified into 4 categories:

• Marginals or Bog pond plants that naturally grow on the edge of a pond or are slightly submerged. These are the best plants to include in a Koi pond if your aims are to beautify the pond, blend the pond with the overall garden and have ease of maintenance and growing. I plant these in pots and place them, half submerged, in the shallower part of the pond. The aim is to keep the soil and roots moist but with the main parts of the plants above the water surface.
• Submerged plants or Oxygenators that provide a pond (or fish tank) with oxygen through the natural process of photosynthesis. These plants would be nice in an aquarium or fish tank but not recommended for a Koi pond.  They will not survive in a Koi pond. Koi eats plants!
• Floating plants or Floaters that floats on the water surface. They multiply rapidly and help to keep algae and water temperatures down. However, they are not suitable for a pond with Koi. Koi tends to eats the roots and shred the leaves. In fact, they love the roots more than the leaves. So, floaters are best grown in a water garden that contains only small fishes.
• Water lilies and lotus that grow submerged under water but with floating leaves and/or leaves that grows above the water. Water lilies need regular fertilisations to keep them blooming daily, so growing them a pot that can be easily accessible is best. The pots are placed in water of about 24 inches depth. They are best kept in still water, away from any venturi pipes or waterfall that will cause ripples or disturbance at the water surface. Large Koi tends to dig at the soil around the plants. A top layer of pebbles or stones large enough to cover and protect the soil is needed in the pot. They are best grown in a water garden that contains only small Koi/fishes or in a water garden that is separated from the main Koi pond containing large Koi.

In summary, if you want both Koi and plants in the same pond, stick to marginals or bogs plants. If you want to include water lilies and lotus, find some means to protect them.

How to solve water quality problem in my Koi pond?

This is a question I often get from my friends after they have seen my pond or heard that I am a Koi keeper.

Many pond owners have built their first pond without understanding the need for a proper pond filter system. Often, these are DYI ponds or ponds build by housing contractors with little experience in Koi pond construction.  They fail to understand the need for a proper water filter system, specially designed for Koi fishes. A Koi pond without a proper filter system would often results in pond water quality problem.  Symptoms would be murky or green water that looks like pea-soup, unhealthy or dying fish, foul smell and all these despite regular back-breaking pond maintenance tasks.

Although water additives would often help fix the symptoms, the long term solution would be to invest in a proper Koi filtration system. Best is to plan, design and build it right the first time. For cases where the pond is already constructed, I guess the most practical way to solve your pond water quality problem is to install an external pond filter system. This avoid costly and time consuming reconstruction of the pond and reduce risk of losing your fish during the process of upgrading your pond.

A good filter system would have mechanical filtration, biological filtration, AND  allows for ease of regular filter maintenance (like backwashing of filters, partial water changes). If your budget permits, choose one with UV steriliser system that helps to kill parasites and algae cells in the water (cause of green water). Some even employ a vortex, centrifugal system to draw solid particles to the center of the filter for more efficient mechanical filtration. These external filter systems come in various models and design to suit the capacity of your pond and your budget. 

Even with a proper filter system, do perform your regular partial water changes to remove the nitrates.

Pond Aeration

Koi needs oxygen and so does the bacteria in the biological filter. Dissolved Oxygen level of 8 mg/litre in water temperature of about 25 deg C is almost ideal since it is almost at saturation point. I used a TetraPond water test kit to measure this. Plants (including algae) in the water also uses oxygen at night. Plants take in carbon dioxide and produce oxygen only in the day, during photosynthesis.

Besides the natural absorption that occurs at the pond water surface, any ways to agitate the water artificially will increase the oxygen absorption by the pond water. Pond designers often include a waterfall for aesthetic reason, as well as for pond aeration. Waterfalls also create the soothing sounds of gurgling water in my home. Waterfalls are ideal for informal pond design. Plants and rocks formation can create a beautiful natural setting. In the picture of my second pond (below), my waterfall is almost fully hidden by the plants (a large bird-nest fern, money plant(Epipremnum aureum), water pennywort and backed by heliconia rosetta).

In my third pond, I used a pot of over-flowing water that sits on a shelf. This then cascade down into the Koi pond through a small step down, bounded by pandan plants(Pandanus amaryllifolius). Other forms of water-feature designs are commonly used as well in Asia, most with feng-shui themes.

Some pond keepers uses an air pump with an air-stone (normally placed within the filter chamber to create streams of bubbles before the biological filter chamber). I don’t use this method in my ponds.

Instead, I use the venturi pipes (picture above). The venturi pipes are very cost effective in aeration. Water from the return pumps are forced through the venturi pipes at high speed and draws air down the air vent to create lots of bubbles at the outlet.

The 2 photos on the top show the construction of my venturi pie. One photo shows the view as seen from the outlet.

Placement and location of the venturi pipes is important. Where feasible, the pipes are arranged to circulate water slowly in a clockwise direction around the pond (circulation is supposed to be good for Koi) and moves dirt and debris in the pond towards the bottom drains using the centrifugal effect. The pipes should be placed about 4 to 6 inches below the water surface, not too deep as it will not work properly if placed too deep (unless you have a strong enough water pump!)

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.

Pond Location – My Third Pond

I have the opportunity to built my current and third Koi pond when I sold my corner terrace house and bought a 10-year old detached house in early 2007. I bought the house with the intention to extend the building structure to create additional bedrooms and living space for my family and of course, a new Koi pond!

The plot of land for the house is a longish, rectangular shape, 10m x 50m in size. I have appreciated the benefits of locating the koi pond close to the living areas of the house from my second pond. Hence this is a key consideration in the design of the layout  for the new building and location and shape for my new Koi pond.

We decided to locate the new pond next to my dining room and have it integrated into the building structure. This means the pond design has to be practically rectangular or squarish in shape, i.e. a formal pond.

 

The dining room is designed with glass folding doors on one side and glass sliding doors on another side which can be opened to bring the “outdoors” into the house. A water feature is constructed next to the dining room. It serves as a water return from the filter. Water from the return pump located in the filter comes out of a venturi pipe and also a large brown pot. Water coming out the pot signifies “overflowing abundance” which is a good feng-shui feature. It also provides the soothing sound of trickling water. For the koi, it provides the needed aeration.

A wooden bridge is laid over the pond to link the Dining room to a new “Entertainment room” on the other side of the pond. The pond circles around the Entertainment room. This creates the illusion that the Entertainment room is “floating” on the pond or some may say sunken into the pond.

 

My water garden is at the back of the house, and can be viewed from the Entertainment room. It houses some small Koi and water lilies. This part of the pond (water garden) is physically separated from the main Koi pond, although they share the same biological filter. Large Koi eats water lily and will tends to dig at the soil and muddied the water!

Pond Location – My Second Pond

I have the opportunity to build my second pond when I purchased an old corner terrace house. As I was doing some A&A (Alterations and Additions) to my newly bought house, it gives me now the flexibility to include a pond into the overall plan.

The backyard in the new house is small, so no more backyard koi pond this time. Instead, my new corner terrace has space at the side and also a relatively large front yard.

We decided to locate the Koi pond at the side of the house, as close to the building as possible, so that we can enjoy the views of the Koi from the dining room (left of picture below). Large sliding doors at the dining room can be opened to bring us closer to our garden pond from the dining room.

View of Koi pond from the dining room.

The pond included a waterfall to provide oxygen for the Koi and to provide the soothing sound of cascading water for the humans. In the picture above, the waterfall is behind the large bird-nest fern and overgrown with money plants and pennywort. Feng Shui tip: The location and facing of the waterfall is such that the water must flow towards the house.

Building tip: If you are building your pond close to the house, I would suggest that you get an architect and/or qualified person (QP) to review the foundation of the house during the pond design and before the construction. Deep excavation close to the house may affect the building structure.

Lesson learnt from my first pond – filter design

Being my first pond and also due to space constraint, the design of my first pond filter has many shortcomings and areas for improvement. These are the lessons learnt and features which was incorporated into my second pond filter design and third pond filter design.

Separate Drain and Pump Chamber

My first pond’s filter (above) does not have a separate chamber to house my drain pump. I need to stop the pond water return pumps during maintenance and turn on the drain pump to remove water from the filter into the drain. That is not a big issue.

The bigger problem is with this: when I removed the 3 standpipes in my pump chamber to flush the dirt from the bottom of my filter, the waste water and dirt from the bottom of the filter chambers are mixed with the regular water in the pump chamber. I need to flush out all the water in the pump chamber before I can turn on the main pumps again. This makes the process of removing the waste from the bottom drains of the filter not efficient and unless I remove a substantial amount of water, some of the dirt are circulated back to the pond. Filter maintenance and water changes take about one hour.

A better design, which was used in the filter for my second and third pond, is to separate the drain/sludge chamber from the return pump chamber as shown below.

Instead of using standpipes, ball valves are used to open and close the bottom drains. The photo (actually from my current pond filter) below shows a sludge chamber with drain pump and ball valves in operation.

A long PVC pipe, with tailored ends as shown, allows the valves to be operated easily from above.

With this design, I can continue to operate my main return pumps while I extract waste water from the bottoms of the filter chambers. This facilitates easy and efficient partial water changes and clearing of the waste collected at the bottom of the filter chambers. It is so easy that which I can do this almost daily or at least weekly.

Need for mechanical filtration or settlement at the filter inlet

Due to space constrain in my backyard, my filter does not have many chambers. In the case of my first filter, my filter mats act as a mechanical filter in the first chamber. This means that the filter mats gets choked after a few months. The symptom is lowered water level in the pump chambers. When these happens, I will have to remove all the filter mats from the first chamber for cleaning, and thereby disturbing the bacteria essential for biological filtration. Quite a lot of work for me too. Not good. Unfortunately, the filter for my second pond did not provide for a mechanical filtration in the first chamber as well.

My third pond filter did! It has a chamber (photo below) to allow for solid waste to settle before going into the filter media. Visible at the bottom of the settling chamber are the inlet pipes from the pond’s bottom drains. Standpipes can be inserted into this inlets to close them off during filter maintenance.

After the settling chamber, the first stage of the filter provide mechanical filtration by using brushes. This is to trap solid wastes and debris like fallen leaves which can then be removed and hosed down when needed.