DIY Modern Backyard Koi Pond On A Budget

7 Materials
$1325
3 Days
Medium

I’m a fish guy. My wife thinks it’s weird and when I say it like that, I have to admit that it does sound a bit odd! For the last 15 years, I’ve wanted to have a koi pond in my yard, but haven’t been able to because we were renters for the first 10 years of our marriage - and most people frown on digging a big hole in their yard and filling it with water. 5 years ago we bought our first house with plenty of property, BUT there wasn’t a place to put a pond where it could be enjoyed. Luckily that all changed as we removed the decks that came with the house and opted for a smaller cement patio. Now was my time to draw up my plans for a koi pond. I marked out an area and convinced my wife that it would be a centerpiece (that isn’t anywhere near the center)…and she approved! After getting the concrete patio poured, I didn’t waste any time digging into the pond project - literally.

DIY Modern Koi Pond

The following video shows the choices I made, problems I encountered and workarounds I developed to create this modern koi pond. I’ve had a lot of feedback and questions about building this pond, so I’ve decided to write out the step-by-step process below. Because I hadn’t planned on making a step-by-step guide for this when I built it, I don’t remember every exact detail for my cuts, but most of it will be obvious when you lay it all out. It really wasn’t very hard to put build and costs will vary based on the size of your pond and the stone or rocks you choose to use. 


Items needed for this build:

1 - 20’x20’ 45 mil EPDM Pond Liner (I bought 20’x25’ to be safe)

22 - 1’x2’ Paver Stones

2 - 1’x6’ rectangular stone (or 3 more of the 1’x2’ pavers above)

4 - 80lb bags of concrete ( I think I only used 3 of the bags…but I can’t remember now)

1 - Pond Filter (I bought and recommend the Laguna Clear Flo 2000 Filter Kit: http://amzn.to/2rBmJ8k)

1 - 20’ of 1” hose (or whatever size is needed for your filter). You may need more depending on where your filter and waterfall are located in relation to your pond (other stones and rocks around it as desired).

4 - 2'x10'x12' boards that I repurposed from the deck I removed

THE PLAN

First things first - know where you want your pond to go and what you want to get out of it. If you are going to build one exactly like mine, I’ve done this part for you. If not, ask yourself a few questions. Is it going to be a koi pond? How many koi or goldfish do you want to keep? This will help you determine the size of your pond. Then you have to take into account your location and what type of winter you have. If it gets really cold and will freeze over, you’ll have to increase the depth of your pond and possibly install a heater. We had a pond in my parents’ yard in Michigan when I was growing up and the fish and water lilies would survive the winter without a heater because the pond was over 3 feet deep and we kept an opening in the ice where water was recirculating - just one more thing to take into account.


I knew from the start that my pond was going to be more about the koi than about the plants - which is good because koi like to eat and destroy the live plants. This also meant that I wanted the pond to be fairly large to accommodate more koi due to their size and bioload. Also, I was trying to work within a given space aesthetically to fit with our patio, pool, and fire pit area. I did stretch it to the max on all sides to make sure I got it as big as I could. 


Even though the koi do nibble on the water lilies, I knew I as going to incorporate them anyway, so I drew in a shallow section that had shelves to accommodate plants which like to be closer to the surface. 

Now that I had my plan, the next step was to measure it out and start digging. 

START DIGGING

To dig by hand or not to dig by hand? That is the question. The whole time I was drawing up the pond in my head, I was thinking about how easy my neighbors backhoe was going to make this project. Unfortunately, the location of the pond only gave us one way to bring the backhoe into the yard and that would require repeatedly driving over our septic system - that wasn’t an option. Hours of backbreaking shoveling later…we had a hole big enough to be our pond. Honestly, it really wasn’t too bad to dig by hand and I got to enjoy the time with my 6 year old son, Dominic, who really wanted to help dig. The soil wasn’t too bad and we didn’t encounter any big rocks. 

TIP: If you can incorporate the dirt into the waterfall feature, it really saves time to incorporate the dirt rather than having to haul wheelbarrows away. In my case, the land where we put the pond had a bad slope and we used the dirt to built up one of the walls and build a mound/berm behind our waterfall. I then planted tall grasses on the berm to create a barrier that would keep your eyes focused on the pond area instead of looking into the great beyond.  


While digging, for the most part, I just eye-balled the interior wall and shelves in my design. I rounded the corners a bit because I knew that liner was going to have to fold or tuck in them anyway. The top paver stones would make the straight line needed visually (thought I did a pretty good job eye-balling it). Most of my time was spent on the top edge of the pond. For the modern design, the top of pond wall needs to be level so that the paver stones will sit evenly around the edge. This proved to be very difficult. Luckily for you, I spent a lot of time trying different things until I came up with a solution that has worked well so far. Once I got the ground close , I put a rim of 2x8 boards around the perimeter that the stones would sit on to keep them uniform. Then I just had to get the boards level with a firm foundation under them. I would then put the liner over the board and the paver stones one top. 


Because my pond was so close to my house, I opted to make one edge lower than the rest of the pond as an overflow away from my house. Because we get some heavy rains associated with tropical storms and hurricanes here in Virginia Beach, there is a good chance that it could overflow - and recently did. I also buried corrugated pipe in dirt along the channel between the pond and house to move the water along the house and out behind the waterfall mound into the main yard (shown in the video).

TIP: Think ahead about where your filter will go. I cut a cap in the boards in the corner by the house on the waterfall side. I have power there and I knew that the filter would also sent water to the waterfall which dictated placement. The gap in the boards under the liner allows the power and hoses to go under the paver stone that will cover them. 

INSTALLING THE LINER

I bought my liner after I started digging. If you are going to stick to your design plans, it wouldn’t hurt to order it first. If not, make sure there isn’t any rain in the forecast before you start digging! it would be horrible to have your dirt walls cave in due to rain. 


The internet makes it easy to calculate the amount of pond liner you need. You insert the length, width and depth into an online pond liner calculator and it will give you the dimensions you need to order. They usually add on 2 feet of overlap for the top size of your pond, but I ordered a few feet extra length. For my pond it suggested a 20’x20’ liner, but I chose 20’ x 25’ because I was initially going to have a basin filled with rocks at the top of the waterfall. I don’t mind having extra liner that I can use as a patch or to modify my waterfall later. 

Putting the liner in was a practice in patience. To start, lay the liner in position over your pond and push the corners and shelfs into place. It looks awful, but keep going. Do your best to tuck the corners into a single fold then put on your bathing suit and have extra hands and some heavy rocks or objects ready to assist you. Hop into the empty pond and turn on the hose. As it fills, start pushing out the wrinkles and working to get as few wrinkle and folds as possible. It is helpful to have someone outside the pond who can pull on the liner as you shape it from the inside, placing heavy rocks on the folds you have completed to keep them in place. 

Plan extra time for a little break for the kids to play in the cold water.

DRY FIT YOUR PAVER STONES

With the liner installed, make sure the boards along your edges are still level. Once the 2’x8’ boards around the edge of the pond are verified to be level, it’s time to dry fit the pavers and get them arranged how you’d like them. My goal was to get them to overhang the pond by an inch or two. As you lay them, you will see that a few cuts need to be made.

I used a segmented diamond circular saw blade to cut mine to size and saved the cutoffs to put between the 6’ long waterfall stones to create a gap between them for water to flow out of. Once you have the pavers cut (I think I had to cut 3 or 4 of one) and in place around the pond, it is ready for cement.

TIME FOR CEMENT

The cement will go on top of the liner that is over the boards. The goal with the cement is to lay enough of a base to allow you to fine tune the leveling process and lock them together all the way around so they stay level and don’t fall into the pond. 


I was lucky enough to have a neighbor lend me his cement mixer to make this part of the job go a lot faster. I mixed one bag at a time and used a cement trowel to apply it under the pavers. I pulled back 2 pavers at a time and then leveled them to each other as I worked my way around the pond. During the process, I did have some cement fall into the pond, but it wasn’t a terrible amount and I didn’t worry about it. The only pavers I didn’t cement in place were the waterfall pavers and one that needed a gap in the tip mentioned below. The waterfall stones are so heavy that they aren’t moving on their own, but I may decide to do the waterfall a different way later, so I gave myself the option. 

TIP: When you get to the paver stone that covers the filter hose and power, leave a good size (5”-6”) gap in the cement above the part of the board you cut out. Then put the paver stone on and level it with the surrounding pavers and then remove it and rinse any cement on the paver off. The cement still on the liner will harden and allow the paver to sit level with the others while still allowing you to place and remove the paver as necessary. 


Almost done. Go grab a glass of sweet tea because the hard part is behind you!

FILTER THAT WATER

From this point on, it is a matter of personal preferences. If you built your pond based on my dimensions, then you have nearly 2,000 gallons of water in it and will require a filter that can effectively handle that much water. If you overstock your pond with fish and have it in direct sun (like mine), then you should get a filter rated beyond 2,000 gallons or run 2 filters for pristine water. I’m actually okay with a little green in my water because it hides the unnatural black liner and the wrinkles, but still gives me a clear view of my fish. I also do extra water changes in the hottest part of the summer to help replace some of the water and cool it down. The Laguna Clear Flo 2000 Filter Kit makes water changes and filter cleaning very easy and it is done externally. You will need to purchase enough 1” hose that you can cut it and run one piece from the pump to the filter and another from the filter to the waterfall. The filter is placed outside of the pond and can be buried up to 1” below where the top and bottom parts meet. The pump is place down in the pond with the hose connected between it and the intake on the filter. The outgoing water from the pump will then go to the waterfall or back into the pond. I just wedged the hose between my two 6’ stacked stones as a simple waterfall. It is that simple and necessary. You want movement to your water, otherwise you are making a mosquito breeding factory. The waterfall agitates the surface of the water and increases the oxygen in the water. My current setup has a weak waterfall, so I also installed a fountain pump that I modified to act more like a bubbler. 


The great thing about this filter is that is also uses UVC sterilization to help control the green algae in the water and it is really easy to clean. You don’t have to fish the filter out of the pond and rinse it with a hose. You just uncap the secondary output from the filter, turn the switch to send the water there and pump the two handles on the filter to agitate the filters and rinse them internally. I put a hose on the outgoing water because it is great for watering the surrounding plants with the nutrient rich water. 

ADD FISH AND ENJOY

Now it’s time to add the plants and fish. Right away I added two water lilies, water lettuce and water hyacinth. Typically you want to let fish tanks and ponds “cycle” before adding fish, or use hardy fish that can survive through the cycle and speed up the process. I’ll let you google what “cycle” means to get more details. I bought 30 “feeder” goldfish to put in my pond to help build up the beneficial bacteria found in cycled ponds and didn’t lose any of them due to the cycle (though one was lost when it decided to break my secondary filter pump I used for the waterfall…watch video for more info). If you plan to have a pond and raise koi, I would suggest learning about “cycling” and buy a water test kit that will allow you to see it take place and keep your chemistry in check. It really isn’t very difficult. Other than that, enjoy the sounds and visual beauty that your pond should bring you for years to come!

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Have a question about this project?

3 of 27 questions
  • Katie
    on Jun 24, 2019

    Can you tell me how and what materials you used to create the waterfall from the filter?

  • Janice
    on Feb 22, 2020

    We have a medium size pool that we do no use. Do you think we could convert it into a koi pond?

    • Nancy N Sanchez
      on Mar 9, 2020

      It can be done. Here is my dad's garden in W. Los Angeles. Sadly the large wild cranes (close to 3 feet tall)ate dad's koi so now it is primarily goldfish and two turtles. My sis who is a graduate of Rutgers' Master Gardener program has been working with dad on plant selection... it is a labor of love.

  • Sandy Romberger
    on May 27, 2020

    We bought the same filter. If you put the filter in the ground, don't you have to remove it for winter? We were told it should be put away during the winter.

Join the conversation

2 of 211 comments
  • Patty
    on Feb 29, 2020

    Nice job

  • Ticia
    on Mar 30, 2020

    You did an absolutely fabulous job. We had a small pond when we lived in NY 3 x 5 ft & about 2-1/2 to 3 ft deep. Put in 10 feeder fish and kept the filter & pump running all year round. Of the 10, 6 survived and grew to nearly 17 inches long over the years and looked like Koi; and then, they bred. We were always bringing baby fish to the nearby school's lake. Many creatures came to our yard and some got some fish but for the most part, they survived and it was a beautiful thing. Good luck to all who try.

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