Building a pond can be the most difficult and most expensive part of fish farming. A well-built pond is a good investment that can be used for many years.
The steps in building a fish pond are:
1. Prepare the site
2. Build a clay core (in the case of contour ponds)
3. Dig the pond and build the dikes
4. Build the inlet and outlet
5. Protect the pond dikes
6. Fertilise the pond
7. Fence the pond
8 Fill the pond with water
9 Stock the fish
1. Prepare the site
First remove trees, bush and rocks, then cut the grass in the area where the pond will be made. Measure and stake out the length and width of the pond.
Remove the top layer of soil containing roots, leaves and so forth and deposit this outside the pond area. Save the topsoil for later use when grass is to be planted on the pond dikes.
2. Build a clay core (in the case of contour ponds)
A clay core is needed in contour ponds and is built under those parts of the dike where the water will be above the original ground level. A clay core is not needed in excavated ponds because there the water level is below the original ground level. Remove all the topsoil in the area of the pond dikes and dig a ‘core trench’ in the same way as you would dig the foundation for a house.
The trench needs to be dug out along the lower side of the pond and halfway along each short side of the pond . Fill the trench with good clay. Add several centimetres of clay at a time and then compact it well. This will provide a strong foundation upon which the pond dikes can be built.
3 Dig the pond and build the dikes
Use the soil that you dug out when making the trench for the clay core to build up the dike on top of the core trench. Try not to use sandy/rocky soil or soil that contains any roots, grass, sticks or leaves. These will decay later and leave a weak spot in the dike through which the water can leak out.
Keep compacting the soil at regular intervals while you are building the dike. After adding each 30 cm of loose soil trample it well while spraying water on the dike. Then, pound it with your hoe, a heavy log, or a piece of wood attached to the end of a pole.. This will make the dike strong. The best slope for the pond dike is one that rises 1 metre in height for every 2 metres in length.
4 Build the water inlet and outlet
The water inlet consists of a canal to bring in the water, a silt catchment basin, and a pipe to carry water into the pond . By widening and deepening the inlet canal right outside of the pond dike, the soil will settle into this hole – called a silt catchment basin – instead of entering the pond. The water inlet pipe runs from the catchment basin through the pond dike into the pond. It should be about 15 cm above the water level so that the incoming water splashes down into the pond. This will prevent fish from escaping by swimming into the inlet pipe.
Pipes should have screens to stop fish from entering or leaving the pond. The INLET pipe is screened at the edge, which is outside the pond to stop wild fish and objects like branches and leaves from entering. The OUTLET (also called drainage pipe) is screened inside the pond to stop fish from escaping.
Screens can be made from many types of materials. Anything will do that allows water but not small fish to pass through :
A. Piece of metal with holes punched in it
B. Screen or wire mesh
C. A clay pot with holes punched in it
D. A loosely woven grass mat
5 Protect the pond dikes
When the pond dikes are finished, cover them with the topsoil that was saved when digging the pond. On the dikes, plant grass such as Rhodes grass (Chloris gavana) or star grass (Cynodon dactylon). Do not use plants with long roots or trees because these will weaken the dikes and may cause leaks.
6 Fertilizing the pond
The natural fish food production in the pond can be increased by the use of fertilizers such as animal manure, compost or chemical fertilizers. Spread the fertilizer on the dry pond bottom before filling the pond with water. Add fertilizer to the pond water at regular time intervals, preferably each day in the late morning or early afternoon. This continuous adding of fertilizer will ensure a continuous production of natural fish food.
If the soil is acid, add lime or wood ashes to the pond bottom in addition to fertilizer before filling the pond. Use 10-20 kg of lime or 20-40 kg of wood ashes for each 100 m² of pond bottom .
7 Fence the pond
Putting a fence around the pond will protect children from falling into the pond and it can help to keep out thieves and predatory animals. To make a low cost and sturdy fence, plant a thick hedge around the edge of the pond or build a fence using poles and thorn branches.
8. Fill the pond with water
Before filling the pond, put rocks on the pond bottom at the spot where the water lands when coming in from the inlet pipe. This will keep the incoming water from making a hole and eroding the pond bottom. Then open the inlet canal and fill the pond. Fill the pond slowly so that the dikes do not subside due to uneven wetting. While the pond is filling, the water depth can be measured with a stick.
Stop filling the pond when the required depth is reached. To prevent overflowing, do not fill the pond too full. Water in the pond should not flow through (and should thus be stagnant), because water flowing through the pond will slow down fish growth by flushing away the naturally produced fish food.
9. Stock the fish
Wait 4-7 days before stocking the fish. This allows the natural food production in the pond to reach a sufficient level to sustain fish growth. In case you decide to introduce substrates in the pond, you will have to wait longer until the substrates are colonised by organisms that can be eaten by the fish. Stock the baby fish (called fingerlings) gently .
( Note, the temperature of the water the fingerlings come from should be about the same as the water temperature in the pond. )
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