Build a Koi Pond - Step by Step Guide

Koi ponds have variations in equipment due to the following:

  • Surroundings - Are there threes in the area? You may need a skimmer. Rocky Soil? Make sure to use underlay material to prevent holes in your liner;
  • Sun Exposure - Are you getting full sun to your pond all day? Make sure you have sufficient filtration – both Mechanical (UV) and Biological (Bio Media) to prevent heavy algae build up and green water;
  • Size Of Pond - A larger pond makes it easier to keep your water levels balanced and also allows you to keep more pond fish and koi. Building a larger pond also means larger equipment is usually required, like pumps and filtration and liner. A 4ft depth at one point of your pond also allows you to keep koi and pond fish over winter in your pond;
  • Quality Of Pond - Do you want as little maintenance as possible when it comes to your pond? There is a filter or product to keep your pond clean with very little effort! Think - having to net out leaves yourself VS a skimmer that can do the job for you! OR clean out filter pads yourself VS a filter with a backwash system.
10 Steps To Build A Pond

Step 1: Plan Ahead

  • Pond placement is key: steer clear of trees with heavy root systems & electrical lines;
  • Look for an area with either part sun or full sun if you are planning to keep fish and/or plants.

Step 2: Excavate

  • Outline the pond perimeter and where components of the pond like the skimmer, falls and filtration will be placed using marking paint;
  • Begin excavation by digging tiers/shelves – the bottom tier should be at least 4ft deep to accommodate fish over winter.

Step 3: Place Equipment

  • Place and backfill both the skimmer and the spillway. Rough out the placement of the flex pipe, and the pressurized filter (usually in behind the falls).

Step 4: Underlay/Liner

  • Line the entire pond and falls area with underlayment then 45 mil EPDM Liner;
  • Ensure liner extends beyond the perimeter by 1 ft to allow for settling earth and rockery over winter. Also extend Liner behind your waterfall to prevent water from escaping.

Step 5: Adhere Liner

  • Attach liner using lap sealant to the skimmer. The Nuts and Bolts will be provided with the skimmer;
  • Attach liner to upflow spillway (lap sealant/nuts and bolts) or have the liner come in behind the spillway if there is no face plate.

Step 6: Rock In

  • Begin placing your rockery/stone. Start with the larger pieces and work down to the smaller pieces;
  • Edge stones should be worked into the first shelf of the pond and also on the top surface to hold the liner in place.

Step 7: Foam in Stream

  • Use waterfall foam in the stream and near the spillway, between the rocks, to avoid water from disappearing through the stones as it travels.

Step 8: Connection

  • Connect skimmer pump to the spillway using PVC Flex pipe and place the pump in the back of the skimmer;
  • Connect the solids handling pump to the pressure filter and from the pressure filter back to the spillway or directly into the pond.

Step 9: Fill & Start

  • Fill the pond with water and add dechlorinator (water prep) and starter beneficial bacteria. Run pumps and filtration and ensure all are running smoothly.

Step 10: Finishing Touches

  • Plant around the pond to create a more natural setting;
  • Fish and plants can be added after a few days once the water temperatures have warmed;
  • Aeration should be added with the fish;
  • Lighting can be added at anytime in or outside of the pond.

Components Of A Koi Pond


Thick filter cloth material is used under liner for protection. Can also be used on top of liner under larger rockery.

Must be installed during pond construction!


EPDM Liner (45 mil) is used to line the pond and behind the falls/stream. This liner is flexible and durable.

Must be installed during pond construction!

Pvc Flex Pipe And Fittings, Glue And Primer

PVC Flex pipe is used to connect pumps to filtration then to the spillway. PVC flex pipe is durable and flexible. PVC fittings are used in pond construction for durability to withstand sunlight and freezing. PVC glue and primer fuse the fitting to the pipe.

Must be installed during pond construction!

Spillway or Up-flow Filter

An up-flow filter or spillway is used at the top of the falls or stream to diffuse the water and provide even falls. An up-flow filter also provides additional filtration once filled with Bio Media.

Must be installed during pond construction!


A skimmer using a skimmer pump draws the surface water into a basket or net to keep the surface clear of debris ie. leaves.

Must be installed during pond construction!

Skimmer Pump

A skimmer pump is a submersible pump that is placed within the skimmer to draw in the surface water and circulate it back up to the spillway.

Must be installed during pond construction!

Pressurized Filter With UV

A pressurized filter cuts down on much of the manual cleaning of the pond. A solids handling pump at the bottom of the pond feeds the bottom water (sludge and debris) into the pressurized filter. The pressurized filter has a backwash system that cleans itself with a few pumps of a handle. A UV system is often incorporated into a pressurized filter to keep the water clear of suspended algae (green water).

Can be added during construction or after construction. Easier to add during construction!

Solids Handling Pump

A solids handling pump can handle small debris and sludge and therefore is placed at the bottom of the pond. The pump feeds the debris and sludge into the pressurized filter and back up to the spillway or directly back into the pond.

Can be added during construction or after construction. Easier to add during construction!


Pond aerators oxygenate your pond water. Every process in your pond depends on oxygen. Oxygen levels drop in higher heat and at night; this is why supplemental aeration is required. Pond aerators also provide oxygen in the winter months. A great way to save energy by turning your waterfall off at night, allow your aerator to oxygenate!

Can be added during construction or after construction!


An ionizer releases ions into the water through a probe which is placed in the pipe line, in the skimmer or in a stream. An ionizer is the only mechanism that can control/eliminate string algae.

Can be added during construction or after construction!

Float Valve Or Electronic Water Level Controller

A float valve or electronic water level controller maintains a constant water level in your pond. It easily connects to a ½” water supply line. These units ensure your pond water never drops too low. Often installed into skimmers.

Can be added during construction or after construction!

Additional UV

Additional UV filters may be needed in a pond if water clarity is lacking. A UV sterilizer/clarifier can be added in-line anywhere from the skimmer pump to the spillway.

Can be added during construction or after construction!


Pond lighting can be used in or out of water. Pond lighting allows you to view your pond at night when most people are home or entertaining.

Can be added during construction or after construction!

Pond De-Icer

A pond de-icer is a unit used to create a small hole in the surface of your pond during the winter months and insures proper gas exchange to keep the fish alive through the winter. These units are thermostatically controlled, making them cost effective.

Must be used during winter months!


Either pond fish or koi can be kept in a pond. If you are looking to over-winter your fish a pond, ensure one part of the pond is 4 ft deep for the fish to go dormant in. A pond de-icer and aerator should be used in the winter.

Let new pond run for at least a week with beneficial bacteria and plants before adding fish. Use a dechlorinator!


Plants provide the necessary shade and hidden cover for fish. They provide oxygen during daylight hours and filtration. Plants are used for decorative purposes to provide a more natural look to any pond.

Add only once the water temperature has become equal to what the plants were accustomed to!

Pond Layout