Affordable 'RAS': The fish farming technology using less water and producing more fish

For decades, fish farming in Kenya has largely relied on earthen ponds.

While the method has helped thousands of farmers venture into aquaculture, it also comes with familiar challenges - high water consumption, fluctuating water quality, fish diseases and limited production.

Now, a new approach known as the Affordable Recirculating Aquaculture System (Affordable RAS) is gaining attention for offering a more efficient way to farm fish.

The technology is being promoted as a solution for farmers seeking higher yields while using fewer natural resources.

What is Affordable RAS?

Affordable RAS is a fish farming system that continuously treats and reuses water instead of constantly replacing it.

Unlike conventional ponds, where fresh water must regularly flow in and out, an Affordable RAS filters the water through mechanical and biological treatment systems before pumping it back into the fish tanks.

This creates a controlled environment where fish can grow under stable conditions.

The result is a system that uses significantly less water while maintaining the quality needed for healthy fish production.

How does Affordable RAS work?

The system operates through a continuous water cycle in specially designed fish tanks.

As waste accumulates, the water passes through filters that remove solid particles and harmful compounds.

Beneficial bacteria then break down toxic substances, after which the cleaned water is oxygenated and returned to the tanks.

Because most of the water is recycled, farmers only need to replace a small portion to compensate for evaporation and routine maintenance.

Why is Affordable RAS attractive to fish farmers?

Affordable RAS addresses several challenges facing fish farmers in Kenya.

The system uses much less water than traditional ponds, making it suitable for areas where water resources are limited.

It also allows farmers to rear more fish in a smaller space because water quality is closely monitored and controlled.

With fewer fluctuations in temperature and water conditions, fish generally experience lower stress levels, reducing disease risks and improving survival rates.

The technology also enables year-round production, giving farmers greater flexibility regardless of changing weather conditions.

How is Kenya using the technology?

Kenya has already begun testing Affordable RAS through pilot projects aimed at improving sustainable aquaculture.

One demonstration project in Nyeri County showed encouraging results, with participating farmers producing substantially more fish from the same farming space than would typically be possible using conventional ponds.

The project has also demonstrated the technology's potential to reduce water use while increasing productivity.

The initiative forms part of broader efforts to modernise Kenya's aquaculture sector and meet the country's growing demand for fish.

Is it suitable for every farmer?

While Affordable RAS offers clear advantages, it also requires a higher initial investment than traditional pond farming.

Farmers need tanks, pumps, filtration equipment and reliable electricity to keep the system operating. Proper training is also essential, as water quality must be monitored regularly to maintain healthy fish stocks.

For many small-scale farmers, however, experts believe affordable versions of the technology could become increasingly accessible through cooperatives, government programmes and private investment.

The future of fish farming in Kenya

As Kenya works to strengthen food security and build climate-smart agriculture, technologies that produce more food with fewer resources are becoming increasingly important.

Affordable RAS represents one of those innovations.

By reducing water use, increasing productivity and allowing fish to be farmed in controlled conditions, the system could help reshape aquaculture in Kenya - particularly in regions where land and water are becoming more constrained.

For farmers looking beyond traditional fish ponds, it offers a glimpse into what the future of fish farming may look like.