A polythene lined fish pond at Nairobi's Langata Men Prisons farm. Embu farmers are using lime to smear the ponds instead of polythene linings to prevent water seepage. Photo by Laban Robert.

A group of fish farmers in Embu County have turned to lime for hardening the walls of ponds as an alternative to the expensive synthetic linings.

Wiyake Fish Farmers Association, which has 60 members, has perfected the art of mixing red soil with lime to create earthen ponds, to reduce water loss.

Clay soil has the highest water retaining capacity. With devolution counties are empowering various group by encouraging fish farming.

But residents of areas having loam or sand soil cannot engage in fish farming because of the water seepage challenge. Such farmers depend on polythene linings to contain the water. The cost of heavy duty polythene lining per metres squire is more than Sh200.

Besides, it is prone to pricking and breakage with time, therefore, requiring regular replacement. Replacements come at a cost to the farmer.

The Embu farmers are mixing red soil with water and lime to make a thick paste that is smeared all round the pond.

The lime not only makes the walls of the pond firm, but also binds the particles together, leaving negligible room for seepage. The thickness of the paste is similar to that used in smoothening the surfaces of mud houses.

The floor and the walls of the pond have to be smoothened out carefully to avoid closing in air particles that will cause cracking. A crack becomes the starting wearing out and exit point for the water.

“We also do a continuous sprinkling with water to ensure that the surface does not dry as we smoothen the pond,” said Mwangi Kihungi, the group’s chairman.
The pond is then filled with water to the brim and the fingerlings are ready to be introduced.

“All our 60 farmers have already adopted the earthen ponds; they are already enjoying fish farming like their counterparts where clay soil is available. The lime lining is a cheaper alternative to the polythene ones, that are unaffordable to small-scale farmers, said Kihungi.

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On may require more than Sh30,000 to purchase a good quality polythene lining for a 10m by 15m fish pond.

Bu the lime required for smearing the same pond may not exceed Sh10,000. The chairman said.

The high prohibitive costs of the new liners have driven other farmers into buying old greenhouse liners.  The liners are not only ineffective in containing the water, with the piercings, but also risky to the fish since they may habour pesticide residues used in the greenhouses.

Martin Miako of Mbeere Constituency lost his entire fingerling stock after using liners bought from a flower farm in Naivasha.

“I just woke up one day to feed the fingerlings and found them floating in the pond,” he said.

At the same time, such linings also have a short life span in this secondhand use.

Tearing starts from the areas buried in the soil as a result of exposure to the sun. Pests like termites may also quicken the weakening of the polythene lining.

Lime, which is calcium oxide, is a strong binding agent.

It is used in stabilising shaky soils during heavy infrastructural construction such as roads and rails. The binding poser of the material bring ensure that the particles are closely packed to reduce the spaces for the passage of water and other liquids.

With the technology, fish farming may be boosted as the ponds can be constructed at the backyards.

The emergency of backyard fish farming is considered secure from thieves and other predators.

A well fenced compound reduces access of the pond by unauthorised people while wire meshes can also stop entry of other predators such as cats, dogs, birds, among others.