Build An Informal DIY Koi Pond In 18 Steps

Excavation

Step 4 – Normal Excavation

The excavation of this DIY koi pond is exactly the same as all the others. However, it is more important to slope the sides slightly because of this particular method of construction. Make sure the pegs remain in position once the hole has been dug.

Reinforcing

Step 5 – Line With Reinforcing Mesh

Once the hole is ready, line it with the reinforcing mesh; this steel reinforcing will make the pond more stable and help to stop it from cracking. Since this is an informal pool with an irregular shape, it will be necessary to cut some of the mesh to get it to fit. You can do this without too much effort if you use a hack-saw or bolt cutters. Bend and then push the ends you have cut into the soil to keep it in position. To ensure an even thickness of concrete, it is useful to insert small chips of brick to form spacers between the mesh and the earth.

Concrete

Step 6 – Mix Concrete

Working in batches, mix together a total of three bags of the cement and approximately 300 kg (600 lb or 8 cu ft) each of sand and stone; the correct amount of waterproofing additive (based on the manufacturer’s instructions) and just enough water to make the concrete pliable. Remember to mix only as much as you can place in two hours.

Step 7 – Slab For Rockery

If you are incorporating a rockery, throw a concrete slab at one end of the pond to form a supporting shelf. If you (or a landscaping specialist) are using GRC panels, it will be necessary to embed a metal pole in the center of the slab to brace and support them. Note that a feature made with natural rocks will require more space than one made with panels.

Step 8 – Shovel Concrete Mix

Shovel the concrete mix into the hole and use a trowel followed by a float to smooth the surface.

Step 9 – Check With Pegs

The completed concrete shell should be about 80 mm (3 in) thick. Make sure that the upper lip is level with the top of the pegs previously inserted around the circumference of the pond.

Step 10 – Spirit Level

Use a spirit level and a water level to check that the upper surface of the shell is level. You can also use a dumpy level, but these are cumbersome and considerably more expensive.

Step 11 – Let Concrete Set

allow the concrete to set for at least 48 hours.

Plaster or render

Step 12 – Finishing And Waterproofing

You will need a good, strong render mix to finish the pond. The remaining cement and sand will give you a 1:3 mix, which is recommended not only for ponds, but for reservoirs and swimming pools as well. It is a good idea to add a waterproofing agent to this too. Use a round trowel like those employed by pool builders to render the pond. Then take a damp sponge and smooth the surface.

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Pump and filter

Step 13 – Pipework & Electrics

Install all pipework and fit any necessary electrical connections before you finish the DIY koi pond or build a rockery. NOTE: While guidelines are given, the factors involved are variable and those DIY builders without adequate experience in this field, should seek assistance from an electrician and possibly also a plumber.
The pump used here is an immersible one, while the filter is hidden above ground, behind the rock feature. The 32 mm (1¼ in) tubing from the pump is routed up behind the rockery with the aid of various connectors. Once installation is complete, the pump will then discharge water into a pre-cast bowl which spills into the pond.