Hanoi’s largest aquatic area shares freshwater fish disease prevention insights

Transition from rice fields to fish ponds

Fifteen years ago, rice fields were replaced by fish ponds as some households built higher dikes, converting their paddies into aquaculture areas. Recognizing the potential of this shift, local authorities at both the commune and district levels designated Tram Long as a key aquaculture zone in Ung Hoa. Since then, fish farming has closely connected both the community and local authorities.

In 2021, the Tram Long Aquaculture Cooperative’s 50 hectares of fish farming received VietGAP certification. However, the certification expired in 2023, and Director Le Xuan Huu chose not to renew it due to high costs and limited economic benefits. Nevertheless, the local community continues to follow VietGAP standards for disease prevention.

Thanks to this, even though fish prices are lower this year compared to last, households that follow the techniques effectively can still earn a profit of 7,000-8,000 VND per kilogram. With an average yield of 25-27 tons per hectare annually, the profit can reach around 200 million VND.

Farms with large fishponds, such as those of Le Xuan Huu (over 4 hectares), Vu Ba Hoc (3 hectares), Nguyen Manh Tuong (2 hectares), and Dinh Quang Linh (2 hectares), have been able to generate significant annual profits.

Huu explains: “The biggest threat now is a virus affecting carp. The symptoms include loss of appetite, sluggish swimming, and fish drifting to the pond banks, dying rapidly—sometimes losing several tons in just a few days. Two years ago, this disease only occurred in spring, but now it can strike at any time, though it is still more common in spring.”

Carp, from fingerlings to market size (2-3 kg), can still die from disease just before sale. This can be prevented with proper care, including monthly environmental disinfection and adding bottom probiotics every 15-20 days to break down waste in the water.

In addition to the virus affecting carp, Huu treats anchorworms every 20-30 days to prevent itching and manages gill fungus to ensure proper oxygen absorption.

Before releasing the fry into the pond, he “bathes” them in saltwater or potassium permanganate for a few minutes to prevent skin diseases. Unlike livestock and poultry, which can be treated with oral medications or injections, aquatic animals are always in water, making them difficult to catch and treat. Therefore, disease prevention is crucial for success.

Previously, some people attempted to crush garlic and mix it into fish feed, but the results were relatively modest. I have found that adding vitamin C to fish food helps enhance heat resistance during the summer, while incorporating minerals and trace elements into their diet improves cold resistance in the winter.

“I’ve been raising fish for so long that I can tell their health by the water’s color. After harvesting two batches, I clean the pond’s bottom, dry it under the sun for 15 days, then apply lime and disinfect it. I only refill the pond when the mud cracks. 90% of the ponds here are built on old rice field soil, with embankments raised, allowing for good ventilation. Draining the water for harvest is convenient, but the downside is evaporation, so we need to regularly replenish the water,” Huu explained.

He avoids using water from his neighbor’s pond and ensures disinfection to prevent contamination, especially when the fish there fall ill, as both ponds share the same drainage and water supply system. He also adds bottom treatment bacteria. As a result, while several ponds in the area were affected by a viral carp disease last year, his pond remained unaffected. By the end of the year, he harvested over 100 tons of fish and made a profit of 1 billion VND.

Father and son share a common goal

Le Xuan Bong and his son Le Quang Khai represent two generations of fish farming in Tram Long, from its beginnings to modern practices. In the past, Bong farmed fish on three acres with no capital or technical knowledge. However, the clean water reduced disease, and despite intensive farming, his yield was only 500 kg per acre, making the effort significant but the profit minimal.

Two years ago, due to his old age, he considered retiring, but his son chose to continue the family business. Starting with a 3-acre pond, Khai expanded by leasing 6 more, bringing the total to 10 acres (about 4 hectares). With adequate capital, he invested 250 million VND in equipment, including a feeding machine, water pumps, and cameras to monitor the fish 24/7, especially since some ponds are up to 2 km from home.

All of these systems can be controlled with a single phone command. On average, he releases biological agents 2-4 times a month to promote microorganisms, treat organic waste, and combat harmful microbes. He also treats for fungi once or twice a month and parasites once.

A team of engineers from the feed production company supports him, testing the water weekly to assess conditions and provide expert advice. Thanks to advancements in science and technology, his fish yield per unit area is double that of his father’s. However, Bong still values the wisdom of the older generation. For instance, he advises limiting antibiotic use. If antibiotics are necessary, he recommends avoiding feeding grass to grass carp, as it weakens their intestines, increasing the risk of rupture and death. He also suggests reducing feed during weather changes to prevent waste and water contamination. Additionally, he recommends stocking fish in a ratio of 70% grass carp, 20% carp, and 10% tilapia to optimize space: grass carp feed at the surface, carp at the bottom, and tilapia help clean up waste.

VFM