“Assembly of the
“Decomposition of algae
Eric Bett
Lake Victoria
Mercy Njeri Estates
Methodist Bio-Intensive Agricultural Training
Nathan Irungu
Smart Harvest

Raised ponds have multiplied my fish earnings: Teacher

Farming was Nathan Irungu’s childhood dream, his efforts to implement the idea was however frustrated by lack of land.

Today, the former primary school teacher at Mercy Njeri Estates, outskirts of Nakuru town is among leading fish producers in the area thanks to raised fish pond technology.


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Irungu, 47, has 14 raised fish pond, farming practised in a greenhouse to regulate humidity and temperatures that range between 23 to 28 degrees celsius.

“This is not just an ordinary greenhouse, this is my fish farm. Green house helps to regulate temperatures in the pond, enhancing growth,” Irungu tells Smart Harvest.

The farmer ventured into raised fish pond production in 2013.

Raised fish pond is a modern kind of fish rearing great for farmers who would want to rear fish but lack space. He leant about the technology at Methodist Bio-Intensive Agricultural Training centre in Meru.

“I learnt about the farming after traveling for a wedding ceremony. As I waited for arrival of the bride, I took a stroll around and spotted the farm at the institution. I had never seen raised fish ponds before,” recalls Irungu.

He got in touch with officials in charge of the project and they connected him to an upcoming training on the same.

To begin within, he constructed a raised fish pond measuring 3 by 8 metres and placed it in a greenhouse and stocked 1,000 flies he had bought at a certified hatchery in Kisii.

After six months of stocking, the farmer harvested his catfish, sold at the local market and used the money to expand his catfish venture. He settled on catfish because they grow faster in higher temperatures and are also hardy (do not require water aeration). The variety also grows fast in higher temperatures.

After the project stabilised, in 2015, Irungu decided to resign from his teaching job to concentrate on fish production.

Advantage of raised fish pond according to Irungu is use of less space and it is easy to manage.

The ponds he adds are also movable, that can enable a farmer move with them from one locality to another.

“Raised fish ponds can be placed on any surface and require no excavation and associated removal of excess soil,” he explains.

Among material required in construction of raised fish ponds include timber, nails, materials that can be locally sourced.

Timber used to construct the pond should be thick for instance 4.5 centimetre and connected using tongue and groove system (a method of fitting similar objects together, edge to edge, used mainly with wood) to prevent leakage of water.

“Thicker timber is used for raised beds to support high water volume and pressure. It is also raised as a security measure,” says the farmer.

Pond liners are also required to provide water tight seal. At local market, a liner costs Sh200 per square meter.

“Standard liners that stand against variable weather patterns and water condition that may be witnessed in production,” he explains.

Before constructing the ponds, a farmer is required to select locality of farming because the material can be heavy making it difficult to move it.

“Assembly of the pond should be done in locality for farming and filled with water,” he explains. A farmer is also required to ensure there is no protruding obstacles beneath the pond to avoid damages.

“A pond width of four feet is a good rule when it comes to raised ponds as this is the maximum reaching distance advisable for safe cleaning and preventing over reaching and potential falls,” adds Irungu.

After construction of the pond, a farmer fills it with fresh water and stock it with fingerlings. Standard stocking is five fish per square metre. The structure is later placed on a raised surface for example cemented block or stone for easier monitoring and safety of the fish.

Among management practices applied by the farmer include draining of the pond after every two months for proper aeration.

Failure to drain the water results into increased level of water Ph that affects acidity.

Acidity he points out is not good with the framing because it kills fish. The water should be fresh from impurities that might also cause diseases.

Growth of algae in production of fish in raised pond is also discouraged because it brings competition of oxygen.

“Decomposition of algae in raised fish pond is discouraged because of breeding. Both the plant and fish require oxygen for growth,” Irungu says.

Pond pump is used to empty the waters to prevent it from becoming toxic from fish excretions.

Farmers who do not have pumps are required to be keen in handling fish to prevent them from being drained out of the pond and dying. As a conservation method, farmers who do not have continuous supply of clean fresh water should tap into rain water harvesting.

“Source of water is major requirement in production of the fish. For me, I have water reservoir of 300,000-litre capacity,” he reveals.

Feeding is also critical for maximum yields. For example catfish are fed once a day on proteins for quick growth, meals alternated with vitamins. To cut on cost, the farmer prefers to makes his own meals using maize, omena, crimps and soya.

“Proteins is highly encouraged and feeding is encouraged in the morning or late evening,” he explains.

Irung’us future plan is to automate water system to be filtered for the filtration purposes to remove residue.

Currently, he sells the fish to small business traders at Ponda Mali market, within Nakuru town and on order.

In addition, the farmer is planning to venture into breeding to supply quality fingerlings and flies to farmers.

For now, he contracts experts who help him with breeding.

As Irungu has demonstrated, fish farming is rewarding if done professionally.

An assistant fisheries officer Eric Bett says monosex type of fish is encouraged in raised fish pond farming to avoid reproduction because of limited space.

“We discourage multiplication of fish in pond as a result of breeding because if they do, they will compete for oxygen that will affect production,” advises the officer.

Bett explains that with growing food insecurity, urban dwellers are encouraged to adopt the venture that require little space.

He notes that the farming is cheap as compared to fish pond that require landscape and soil.

The raised fish pond uses a standalone timber structure that holds water.

“With proper management practices, a farmer is able to harvest table size fish at between six and eight months from the day of stocking,” says the expert.

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