Change beneath the water in Nho Quan: Raising yellow catfish with silver nanoparticles

A new direction as the market grows saturated

When I arrived, Nguyen Duc Hanh and his son Nguyen Van Ban, of Nho Quan commune, Ninh Binh province, were carrying mortar to patch holes in the concrete banks around a pond where yellow catfish had just been harvested. Above the waterline, that was the scene; on the pond floor, they had spread a layer of white lime powder to disinfect the bottom before letting it dry out, ready for the next crop.

Hanh formerly served as Vice Chairman of the People's Committee of the old Lang Phong commune and has just retired under Decree 178, which now allows him to devote his full time and energy to his passion: aquaculture. Whatever the challenges, it is still steadier than raising pigs. An outbreak of African swine fever last year forced the destruction of more than 100 of his family's pigs, a loss of over 300 million dong, and the pig pens still sit empty today.

In 2014, when the locality carried out land consolidation, Hanh and his siblings volunteered to take on 4.7 hectares of land in a field beside the Hoang Long River. At the time, the land was nothing but an uneven series of borrow pits, ill-suited to either rice cultivation or fish farming. He had to hire an excavator to dig and shape it into six ponds, build up the banks, reinforce them with concrete, spread graded stone for access roads, and install water-aerating fans, three-phase electric pumps, and timed feeding machines. Over four grueling years, he mortgaged three of his family's land-use certificates to secure loans, investing 3.5 billion dong in the farm.

Once the infrastructure was complete, he began stocking traditional fish species such as white grass carp, black grass carp, silver carp, bighead carp, and common carp, feeding them a diet that was 80 percent industrial feed and 20 percent grass grown along the pond banks. The farm's average annual output topped 30 tons of fish, but after selling, his profit came to just over 100 million dong. The largest expense was industrial feed. Without enough cash to pay for feed upfront, he had to buy on credit, settling up only after harvesting fish six months later, which cost him an extra 30,000 dong per 25-kilogram bag.

On top of that, the market for grass carp, silver carp, bighead carp, and common carp has been saturated for several years, with prices holding around 42,000-48,000 dong per kilogram even as feed prices rose from 350,000 to 480,000 dong per bag, and traders began demanding larger fish, up from 2 kilograms to 3 kilograms each. Add to that rising disease-treatment costs, electricity bills for running oxygen aerators, lime powder, and biological products, and it is little wonder that of the 19 households farming the 26-hectare aquaculture zone in the old Lang Phong commune, four or five have already abandoned their ponds.

Hearing that the state was offering support for new crop and livestock models, Hanh and his son registered with the Ninh Binh Provincial Department of Science and Technology in November 2024 to carry out a project titled "Applying scientific and technical advances using silver nanoparticle biological products in nursery rearing and commercial farming of yellow catfish in Nho Quan district, Ninh Binh province." The model was carried out on more than 1 hectare. Because yellow catfish tend to burrow and hide, even with concrete-reinforced pond banks, the base of the banks still had to be lined entirely with netting before stocking.

The fingerlings received, at a size of 400-500 fish per kilogram, were not released straight into the pond but raised first in net enclosures, moving from smaller to larger enclosures, and only released into the open pond after 30 days once they reached a size of 120 fish per kilogram. Thanks to an accessory breathing organ, yellow catfish can survive in low-oxygen environments and require far less aeration than many other fish species. Feed used in the model was entirely industrial feed. While small, the fish are grayish in color, but one month before harvest, Hanh switches them to a color-enhancing feed so that after three weeks they turn a bright golden yellow, matching market demand.

In June 2025, he harvested his first crop, with an 80 percent survival rate and output topping 6 tons, sold at 52,000 dong per kilogram for a profit of 150 million dong. In July 2025, he stocked a second crop, harvested in February 2026, with a 70 percent survival rate and 5 tons of output, sold at 44,000 dong per kilogram for a profit of 80 million dong.

Lessons from the field

"Yellow catfish tolerate heat well - the hotter it is, the more they eat - but they handle cold poorly; below 15 degrees Celsius, they barely eat at all. So it's best to avoid raising them in winter, and in summer, feed them more to keep their growth on track. The market for yellow catfish is quite narrow and hard to sell into, unlike grass carp, silver carp, bighead carp, and common carp - right now the only buyers we've found are traders from Hai Phong, since no one locally will buy them," Hanh said, summing up after two production cycles.

His son, Nguyen Van Ban, Director of Chung Hieu Investment and Construction Co., Ltd., said that while yellow catfish offer fairly strong economic returns, they are prone to skin ulcers, lesions, and digestive-tract disease, which can trigger mass die-offs. For that reason, silver nanoparticles should be used during farming, both to treat the pond bottom and mixed directly into feed.

Ponds using silver nanoparticles were closely monitored and compared against control ponds without the treatment, tracking indicators such as temperature, pH, and dissolved oxygen, as well as fish growth rates and health status. In addition, Ban also dissolved lime powder in water and applied it to the ponds to curb the spread of viruses and bacteria. During feeding, he regularly checked for excess feed, since leftover feed can encourage algae growth.

Changing the water once or twice a month also helped control algae growth. As a result, growth indicators recorded in the experimental ponds consistently outperformed those in the control ponds, delivering economic returns two to three times higher.

Yellow catfish (a native Vietnamese catfish species) are indigenous to Southeast Asia. In Ninh Binh province, the species once thrived in the low-lying areas of the old Nho Quan and Gia Vien districts but has gradually become scarce as habitats have changed and chemical use on fields and in ponds and lakes has increased. That is why the model of raising yellow catfish combined with silver nanoparticle products to kill bacteria and viruses in the water has become a new source of hope for the local aquaculture sector.

$ 1 = VND 26,480 - Source: Vietcombank.