How to Build a Koi Lake

The Site of the New Koi Lake

Main Pool of New Koi Lake Before Restoration
Main Pool of New Koi Lake Before Restoration

The Project

When we decided to build a Koi lake it was because we had a number of high quality Koi in our main fishing lake, (Les Rouvets Lake in Guernsey), and we felt they would be a good start to a Koi breeding business. We already had the main lake, but also had a further lake that was a lot smaller and had been unused for many years due to it having long since developed a leak. When we decided to restore it the lake had only a few inches of water in it, was overgrown, and majorly silted up.

This was always going to be quite a big project, but we were keen to do this as we wanted to avoid our Koi being fished for, at the same time as utilising them as a sideline business. Many of the Koi we owned were already very large and worth substancial amounts of money, not to mention being prime breeding stock if we did things right.

Before Restoration

Stream Leading into Main Pool Partially Filled.
Stream Leading into Main Pool Partially Filled.
Streambed Before Restoration
Streambed Before Restoration
Streambed Before Reeds and Rushes Cleared.
Streambed Before Reeds and Rushes Cleared.
Middle Pool Before Restoration.
Middle Pool Before Restoration.

The Lake Plan

Beginning the Work

We looked at the existing remains of the small lake and came up with a plan. The lake/ponds currently formed an interesting shape. We had a main overflow from our fishing lake that led into the smaller lake which was a shape not dissimilar to a dog bone. What we actually had was a very shallow pool where the overflow fed in, followed by a stream bed, followed by a small pool, then another stream, ending in a far larger pool that was currently only a few inches deep in water with the rest draining away through the leaks.

We decided that first and foremost we needed to remove a lot of the overgrown tree branches and brambles to allow access to the site for a JCB. This in itself was quite a task as the lake had been neglected for over twenty years, and silted areas were dangerously deep much like quicksand. Never the less, we bravely battled on with the help of a very good friend of ours who had dug out the main lake back in 1963. Now retired, Charlie assisted and advised us throughout the project, and frequently came down to assist with chainsawing, building up banks etc.

Richard my Husband had to wade through the shallow stream bed and cut down the reeds and grasses that were now filling the area, whilst my Stepfather James (a retired fire chief), had the job of going up the trees to cut down the badly overhanging branches to allow more sunlight on to the surface of the lake in addition to many other heavy jobs and manual labour that was needed, (luckily he is a very fit man even in retirement). Charlie meanwhile was up at the lake on a daily basis cutting down further undergrowth and laying ladders across the surface of the silt to enable the team to safely cross the silt without sinking into it.

Bit by bit the area where the main pond was opened up to the point where we could call in the JCB to begin removing the silt, and sealing up the leaks so that we could begin to fill the lake to capacity.

Clearing the Overgrowth

Removing Overgrowth from Main Pool
Removing Overgrowth from Main Pool
Ladders Over Main Pool to Avoid Workers Sinking into the Silt.
Ladders Over Main Pool to Avoid Workers Sinking into the Silt.
Charlie Cutting Overgrown Branches
Charlie Cutting Overgrown Branches

The JCB

We initially diverted the stream away into an adjacent field knowing it would automatically flow down to rejoin it's natural path some way beyond our new lake. We then brought in a large JCB which initially had to build a ramp of solid earth out across the largest pond to enable it to gain access to the silted up areas at the far side, as well as building up the left hand banks. The driver then proceeded to scoop out many tonnes of silt down to a depth of around 12 feet. This silt was used to build up the left banks, along with a large amount of clay soil. As the driver worked backwards bit by bit he gradually removed the earth ramp he had built.

The JCB was then moved on to the middle pool, which again needed to be dug out to remove many years of silt build up. This pool was dug down to a depth of between 4 to 6 feet.

Finally the JCB used a few tonnes of soil to build up the bank at the point where the stream would naturally enter the new lake, and where we ultimately wished to create a path/walkway around the new Koi lake.

The Middle Pool

The Overflow

To create an overflow point was naturally very important if we weren't to end up losing our banks once the stream refilled the lake to capacity. As the stream is only small, it was felt that laying a couple of pipes would be sufficient to cope with any unexpected rainfall or storms, and would ensure that the water could freely drain away as required. We laid the two pipes side by side, and we intend to fit them with downward pointing "U Bends" to take the end of the pipes below water level so that they won't get blocked up by debris from the lake surface. The pipes will then be buried in further clay earth and soil to enable us to sow grass seed over the banks.

We allowed the banks about four days to dry out before we felt it was safe to divert the stream back through the new lake with a view to finally filling it up so we could look at adding the Koi to their new surroundings. During this time reeds and rushes were cleared from the connecting stream beds between the ponds, and the banks that were established were tidied up with petrol driven strimmers and scythes.

Progress Throughout the New Koi Lake Plus Filling with Water.

The Stream Entering the Largest Pool
The Stream Entering the Largest Pool
The Pool where the Stream Enters the Lake
The Pool where the Stream Enters the Lake
A Section of the Connecting Stream
A Section of the Connecting Stream
Connecting Stream Between Pools
Connecting Stream Between Pools
Middle Pool
Middle Pool

Filling the Koi Lake

After the tidying up was complete, we rediverted the stream back into the new lake and waited with bated breath to see if it would fill up okay with no further leakage. After about four to five days the water reached the level of the pipes with no evidence of any problems, (much to our relief).

We called in an expert on Koi and asked him for his opinion on the more or less finished product. He was incredibly impressed and said the whole habitat was perfect for Koi. His reasons for this were that we were providing both sunny areas and shady areas, in a range of good depths, (which are especially important if you want the Koi to develop deep set bodies), there was an abundance of natural food sources such a dragonfly larvae, insects, bloodworm etc and the whole area was essentially pretty vast for a Koi pond with lots of natural plant life both surrounding, and in the water itself. We had also added some waterlilies by now, and these are ideal for the Koi to shelter below or to spawn in. Carp in general also prefer coloured water rather than clear water, and this provides them more protection from predators as they are less visible.

All in all the finished result looked incredibly natural, with trees still growing low over the water in woodland glade type settings, as well as open pools with access to sunshine in other areas. The total length of the new lake including all three pools and both connecting streams must have ended up being around 150 feet, with varying widths from around 10 feet to 30 feet across depending on whether it was a pool or part of the connecting streams. The depths varied between 4 feet and 12 feet depending on whereabouts within the lake or stream it was.

Improvements and Filling with Water Continued

Middle Pool
Middle Pool
Stream Between Middle Pool and Main Pool
Stream Between Middle Pool and Main Pool
Stream Leading into Main Pool
Stream Leading into Main Pool
Stream Coming from Middle Pool towards Main Pool.
Stream Coming from Middle Pool towards Main Pool.
Main Pool where Stream Enters.
Main Pool where Stream Enters.
Overflow Pipes  on Main Pool
Overflow Pipes on Main Pool
Main Pool
Main Pool
View Across Middle Pool from Opposite Side
View Across Middle Pool from Opposite Side

Cosmetic Touches

The hardest part was now done, but we still had to grass seed the banks where the JCB had laid fresh earth, and we also wanted to add in a wooden bridge to allow easy access from one side of the Koi lake to the other. We intend to create a viewing platform where people can simply sit and watch the Koi feeding. On the far side of the banks we want to create a small woodland path running alongside the lake so that it wil be possible to walk the entire circumference of the lake before using the wooden bridge to cross back over again.

For a little while at least the new Koi lake will look like a bit of a building site in places as grass takes time to grow and get eastablished, but the finished result will look fabulous and very natural.

Introducing the Koi

Having given the lake a week or two to settle down, we began adding Koi from our main lake to see how they got on. Normally a new lake would require some weeks or even months before you could add fish, but we had the advantage that the site had never completely dried up before, so the natural foods such as the bloodworm had continued to survive below the surface, as well as our already having well established plants around the lake that would drop insects into the water immediately.

The first eight Koi were introduced to the lake on the 21st July 2008, and by the next day they were happily basking in the sunshine in the pool nearest to the main lake where the stream initially enters, no doubt also enjoying the oxygen that the running water provided. Already they had been seen jumping for flies and were happily feeding on Koi pellets that we threw in.

Over the next few weeks we continued to catch and transfer the Koi from our main lake into the new lake, as well as adding around 30 very large, high quality Koi that we were given by the expert who complimented us so highly on the conditions we had created. The end result was the new Koi lake containing around 80 large Koi in a wide variety of colours. A very spectacular sight to see when they are all feeding at once.

The satisfaction this project has brought is immense, and we now intend to begin our breeding program with a view to selling on the babies once they reach respectable sizes. Of course breeding Koi is going to require "Green Ponds" to hold the eggs and fry so they are not eaten by the larger fish, therefore I am guessing our next smaller project will involve creating these green ponds before the next breeding season arrives.

Koi in the New Lake

And Finally

Due to the nature of the shape of this Koi lake, and the fact a large part of the water is concealed by the treeline, it is impossible to capture the finished result all in one photograph, so I hope you can use your imagination to mentally "connect up" the pictures I have provided and using the diagram of the layout can visualise the overall lake and the surroundings. Naturally there will be further cosmetic touches added, and it will take a while for final viewing platforms to be built and the grass seed to grow, but the good thing is that the Koi are already thoroughly enjoying their new environment and could not ask for better conditions to thrive in.

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Comments 19 comments

Bard of Ely profile image

Bard of Ely 8 years ago from Lisbon, Portugal

That's a fantastic natural environment you have given the fish, Cindy! I am not surprised you are proud of your achievement!


mistyhorizon2003 profile image

mistyhorizon2003 8 years ago from Guernsey (Channel Islands) Author

Thanks Steve, the fish seem to love it too!!!


starrkissed profile image

starrkissed 8 years ago from Arizona

This is so neat. I just learned about Koi ponds through a girl that is in one of my volunteer groups. Well, not a girl, a woman, but anyway -- she has just finished with her first Koi pond and she's all excited.


Nicole Winter profile image

Nicole Winter 8 years ago from Chicago, IL

Wow, amazing work, guys! Absolutely stunning, ya'all really put yourselves out there making this happen and the end results are fantastic! Give yourselves a pat on the back for me!


mistyhorizon2003 profile image

mistyhorizon2003 8 years ago from Guernsey (Channel Islands) Author

Thanks Starkissed, I am sure your friend is going to have great fun with her Koi, it really is quite addictive.

Thanks to you too Nicole, it is really getting there now, and we have just been offered another 30 Koi valued at £50,000 free of charge because the owner is moving aborad and is so impressed by the conditions we can offer to them. We have also now added a quaint arched wooden bridge to the Koi lake, so I shall try to take a photo soon and upload it to this hub.


Brainstormer profile image

Brainstormer 8 years ago from Australia

Don't be Koi about this. You done great.


mistyhorizon2003 profile image

mistyhorizon2003 8 years ago from Guernsey (Channel Islands) Author

Ohhhh, Brainstormer, that is so bad!! :)


Alison 8 years ago

What a beautiful pond you've created. It will bring you and your family a great deal of pleasure. I have only a small formal pond with goldfish and aquatic plants but I enjoy many meals beside it during summer.


mistyhorizon2003 profile image

mistyhorizon2003 8 years ago from Guernsey (Channel Islands) Author

Thanks Alison, the fish seem to love it, and so far we have only lost one to a Heron, and that was a small one. Since then we have put up nets to make it harder for the Heron to hunt.


johnsocrates profile image

johnsocrates 7 years ago from Kalibo, Aklan

populate koi and populate beautiful; creatures in the world. this article is really awesome! for more about koi visit www.mypetkoi.com


hypnodude profile image

hypnodude 6 years ago from Italy

Wonderful pictures. If I'll ever have the place for it I'll follow your instructions. Great hub.


mistyhorizon2003 profile image

mistyhorizon2003 6 years ago from Guernsey (Channel Islands) Author

Thanks hypnodude, they are in a beautiful location and breeding very happily now.


Tony Bevington 6 years ago

followed through from the other section and its hard to know what to do for the best.I had wanted to create a 'natural' pond.But Koi and their like seem to offer the potential to make some money from my new pond and now I have decisions to make.You dont mention Herons.How do you avoid their hunting your ponds.


mistyhorizon2003 profile image

mistyhorizon2003 6 years ago from Guernsey (Channel Islands) Author

Hi Tony, Herons on the Koi pond are not a problem as it is surrounded by thick woodland and they cannot land in an area that would allow them to easily take off again if a predator approached, therefore they don''t risk it. The one end used to attract them because there was room and the water was shallow there, but we put loads of old branches and barriers around the sides and now they can't access that part either. In the main lake they do land in the shallow end where the silt has built up, and to be honest there isn't much we can do about that except hope the large Carp stay out of their way and they only catch the fry (of which we have millions).

The only suggestion I could give you to keep them off a smaller domestic size pond would be to put about 6 short bamboo canes around the perimeter of the pond and then stretch fishing line from cane to cane starting at about 6" off the ground with a second line about 12" off the ground. The advantage to this is that the Herons are waders, and when they try to step into your pond or up to the edge of it, the fishing line puts them off because it acts like a trip wire. They will probably look a little confused and then fly away, (it worked on my parent's pond). The other good thing is the fishing line is virtually invisible so is not an eyesore to look at and it means you don't have to cover the surface of your pond in mesh.

To be honest I reckon Cormorants are far more of a danger to your fish as they land on the water and dive down after the fish, and do a lot of damage to larger fish when attacking them even if they don't manage to kill them. There is nothing I know of you can do to get rid of them, but fortunately you only usually get one at a time.


Fluffy77 profile image

Fluffy77 5 years ago from Enterprise, OR

Your voted way up here! I'm a big fan of both coy and ponds, you did great work here with this topic.


mistyhorizon2003 profile image

mistyhorizon2003 5 years ago from Guernsey (Channel Islands) Author

Thanks Fluffy. The pond is still going strong and people keep giving us their Koi when they decide to give up keeping them. We have some in there that must be well over 25lb in weight and are huge. Clearly they are very contented as they keep spawning ever year.


mistyhorizon2003 profile image

mistyhorizon2003 4 years ago from Guernsey (Channel Islands) Author

Hi Janie Graham, please can you post your comment again without the link, and then I can approve it as not being SPAM. Thanks.


Aidan Hamburg 6 months ago

Hey I was thinking about starting a Koi pond, and if I were to have something like 7 Koi, how many gallons would that be and how deep should it be?


mistyhorizon2003 profile image

mistyhorizon2003 6 months ago from Guernsey (Channel Islands) Author

My advice is to give them as much room as you possibly can. I can't really calculate it in gallons as our Koi lakes/ponds are naturally filled by a stream and hold thousands of gallons. What I would say is to make it as deep as you can, ideally at least two metres or more. The depth is important because it allows the fish to go down deep in the colder weather, plus it encourages them to develop deep bodies rather than long slender bodies.

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