Rooibos boosts Tilapia growth in breakthrough study

SOUTH AFRICA – Researchers at Walter Sisulu University have found that adding green Rooibos extract to tilapia feed significantly improves growth rates and feed efficiency. 

The study, led by senior researcher Prof Grace Okuthe, offers a natural, locally sourced innovation with both environmental and economic benefits for South Africa and potentially the global fish farming industry.

The controlled trial compared tilapia fed on standard commercial diets against those receiving feed enhanced with either fermented Rooibos (the familiar red variety) or unfermented green Rooibos extract. 

The findings were striking: fish fed the green Rooibos diet grew 2.83% faster and converted feed into body mass 0.9% more efficiently than the control group.

“These may sound like small numbers,” said Prof Okuthe. “But in commercial aquaculture, even fractional improvements in feed conversion translate into substantial cost savings, faster production cycles and reduced environmental impact.”

How Rooibos works in fish feed

The research team attributes the effect to Rooibos’ bioactive phenolic compounds, which appear to make feed more palatable, enhance gut health and boost nutrient absorption. Beyond growth improvements, the extract also demonstrated evidence of DNA protection in fish, indicating broader health benefits.

“These compounds work in harmony with the fish’s digestive system, helping them get more from the same amount of feed,” Prof Okuthe explained. “It’s not about adding protein or calories – it’s about enhancing the efficiency and resilience of the fish.”

Such improvements address one of aquaculture’s biggest challenges: waste. By improving feed conversion, less uneaten feed and waste enter the water, reducing nutrient runoff that contributes to algal blooms and ecosystem damage.

Economic opportunities and sustainability links

Rooibos, cultivated exclusively in South Africa’s Western Cape, could also bring economic gains if demand for green Rooibos extract grows at a commercial scale. 

A new market for the indigenous crop would support growers, create rural jobs, and align with South Africa’s commitments under the Nagoya Protocol, which ensures benefits flow to Khoikhoi and San communities, the traditional custodians of Rooibos.

“This research shows how an indigenous crop can open new economic pathways,” noted Prof Okuthe. “In addition to the potential economic benefit to the industry, it also supports South Africa’s commitment under the Nagoya Protocol.”

Replacing some imported synthetic feed additives with locally sourced Rooibos extract could lower input costs and reduce reliance on volatile international supply chains, an important factor as global shipping and regulatory costs continue to rise.

Scaling challenges and global potential

While the lab-scale results are encouraging, the researchers emphasize that broader adoption will necessitate additional work. Scaling up would mean ensuring a consistent Rooibos supply, preserving extract potency during feed manufacturing, and validating results across different farming systems. 

Regulatory approvals and long-term studies will also be essential to confirm there are no impacts on fish quality, taste or texture.

The next phase of research will test green Rooibos on other aquaculture species such as freshwater fish and shrimp, opening the possibility of a universal, natural feed additive.

With aquaculture now supplying more than half of the fish consumed worldwide, innovations that boost efficiency while cutting environmental costs are in high demand. Tilapia, one of the most widely farmed species, stands to benefit significantly from such a development.

“South Africa has an opportunity to lead here. We’re combining heritage, science and sustainability in a way that resonates with global markets,” emphasised Prof Okuthe.

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