David Kawahigashi
Vietnam’s rapid growth in shrimp production, estimated to surpass 500,000 metric tons in 2019 (GOAL 2019),has been tempered with immense pressure from the local government, export markets and environmental groups to improve their farming practices to become more sustainable and cost effective.
The Mekong Delta where 80% of the shrimp in Vietnam is grown, has been suffering from waves of diseases outbreaks along with increasingly poor water quality. As a result, failure rates in the traditional earthen ponds has been predominating over the number of successful pond harvests. The challenge to improve both efficiency and sustainability in how shrimp should be produced has been the driving force behind a recent paradigm shift in Vietnam.
The Round-Tank Revolution
The “round-tank” revolution began approximately 3 years ago as a nursery-phase turned grow-out using above-ground tanks. Circular, 100 metric ton tanks as 30-day nurseries have been in use worldwide for many years, but the thought of using larger diameter above-ground tanks for on-grown shrimp seemed unfathomable due to limited capacity.
Through trial and error and refining of management techniques, the advantages of growing shrimp in large above-ground tanks measuring 500 to 800 m2 with center drains was realized. Maintaining a clean pond or tank bottom has become paramount in this day and age of pathogens causing early mortality (EMS/APHNS), white feces disease, and slow growth from EHP.
As the round tank design is the most hydro-dynamically efficient shape to create a circular flow to concentrate waste for easy removal, it made good sense to expand this concept to grow shrimp in larger diameter tanks. 
The Minh Phu “2-3-4 Technology”
Although the round-tank farms are mostly comprised of small, family-owned farms and a few medium scale farms, there is one large company, Minh Phu Seafood Corporation, that has been developingtheir own “corporate farming” model. Minh Phu is a vertically integrated company that specializes in grow-out, processing and export. Originally a small company established in the 1990’s in southern Vietnam, Minh Phu has become the largest shrimp processor worldwide and the largest exporter of shrimp products out of Vietnam.
In 2019, the Chairman of Minh Phu, Mr. Le Van Quang launched their round-tank intensive farming strategy called, “2-3-4 Technology”. The design of the 2-3-4 Technology model consists of a production module covering 8 hectares of 20 round grow-out tanks (32 meters in diameter or 800 m2) and 10 smaller nursery tanks (16 meters in diameter or 200 m2).
The shrimp culture area is divided into two separate grow-out phases, a 25-day nursery phase and a 90-105 day grow-out phase. The round production tanks utilize 60% of the total area of the module and the settling and treatment water reservoirs occupies the remaining 40%.
#2: 2-Phase Grow-out
The “2” in “2-3-4 Technology” implies that the shrimp are grown-out in two phases. The first nursery phase is stocked at two post-larvae per liter or 2,000 PL per m2 of culture area. After 25-30 days of culture, the juveniles are transferred to the larger 800 m2 grow-out tanks. Estimated survival rate from each phase is 90% respectively.
| #2: grow-out phases | Phase 1 | Phase 2 |
| Tank area | 200 m2 | 800 m2 |
| Days of culture | 25-30 days | 90-105 days |
| Stocking density | 2 PL/liter | 300/m2 |
| % survival (estimated) | 90% | 90% |
| Cycles per year | 8 | 4 |
#3: Harvests Per Cycle
The “3” refers to number of harvests per cycle. Each Phase 2 grow-out tank is partially harvested (twice) before the final harvest. The first partial harvest happens after 60 days of culture at 65 to 70 per kilogram (15 grams). The second partial harvest is around Day 85 with sizes in the 50 to 45 per kilo range (22 grams). The final harvest is at 105 days of culture targeting 30 to 25 per kilo (35 to 40 grams).
| #3: harvests per cycle | % of shrimp | # per kilo | Grams | ADG |
| Partial harvest #1 | 25% | 65 to 70 | 13-15 grams | 0.27 |
| Partial harvest #2 | 25% | 45 to 50 | 20-22 grams | 0.32 |
| Final harvest | 50% | 25 to 30 | 35-40 grams | 0.37 |
Above: A partial harvest in a 500 m2 grow-out tank; weighing the harvest
#4: Four Key Principles
The “4” refers to four key principles which are considered essential for a high success rate:
- High performance genetics and post-larvae quality
- Water quality and adequate storage capacity
- Environmentally friendly
- No antibiotics
- High Performance Genetics and post-larvae quality – Securing a steady supply of disease-free and healthy post-larvae is paramount for the financial success of this intensive round-tank farming model.Good quality, high-health post-larvae also include animals that have been sourced from fast-growth genetics. The difference between making a profit and taking a loss in the round-tank model can come down to accelerated growth rates under high density, high biomass conditions.
- Water quality and adequate storage capacity- Water storage capacity covers 40-50% of the module area for good reason. Having the capacity to exchange high volumes of water, up to 100% per day as the biomass approaches carrying capacity, is essential for this super intensive system. Water exchange rates for the full cycle may average just 20% per day, however, the requirement towards the end of the grow-out cycle can be demanding. A dedicated water storage capacity for settling, treatment and conditioning are necessary to insure the quality and quantity of exchange water to maximize grow-out performance of the shrimp.
Above: A series of lined reservoir ponds for each round-tank module
- Environmentally friendly – Environmentally friendly implies to a variety of benefits from this round-tank model. Upmost is the option to recirculate the culture water to minimize discharge reducing the impact to the local ecosystem. Recycling of culture water also enhances biosecurity which in turn reduces the risk of disease manifestation. Moreover, this high-yield, small footprint model would suppress further shrimp farm expansion and would enable farmers to continue farming in the low-lying areas of the Mekong that are at risk of rising sea levels.
- No antibiotics – Unlike traditional farms and intensive pond systems,the need to use antibiotics in the round-tank system is eliminated as the combination of efficient waste removal, probiotics and good water quality optimizes the culture conditions. Reducing the use of antibiotics in exports would help to improve the image of Vietnam-produced shrimp on the global markets.
Other construction and management criteria
Efficiency is further enhanced with high-quality, high protein feeds, automatic feeders, probiotics, shading of the surface area to minimize algae blooms and recycling of culture water.
Aeration and water movement is provided by a combination of paddlewheels and diffuser tubes powered by a blower. Both automatic feeders and manual feeding are used in these round-tank farms.
As the risk of disease outbreaks and crop failures is significantly reduced using this round-tank technology, more emphasis is placed on providing a high-protein diet to optimize these genetically superior shrimp strains. Feed protein levels begins at 45% and is reduced down to 38-40% protein in the later phases. Feed management is important in maintaining low Feed Conversion Rates (FCR).
| Manpower | 2 worker2 for 6 round tanks (feeding and exchange) |
| Feeding | Manual or automatic feeder |
| Feed | 40% protein minimum |
| Aeration per 500 m2 | Blower – 2 hp per tank; Paddlewheel – 3 hp |
| FCR | 1.2 (up to 20-25 grams); 1.5 (for 30-40 grams) |
| Cost per kilo | $4.00/kg (25-gram shrimp); $3.50/kg (33-gram shrimp) |
The Round-Tank Revolution Continues
Due to the success of the “2-3-4 Round-Tank Technology” model, Minh Phu has been busy constructing round-tank modules in their two commercial shrimp farms over the past two years. The 300 hectare Loc An farm east of Ho Chi Minh City and their larger Kien Giang farm had a combined 1,000+ round-tanks in operation producing over 15,000 metric tons in 2019. Minh Phu and their new partner, Mitsui (from Japan) are planning to expand the farming capacity at their Kien Giang farm to operate more than 4,000 round tanks across 2,500 hectares in the province by 2025 (VietFish, July 2019).
The driver to the round-tank, multi-phase, super intensive systems comes down to the ability to achieve large shrimp sizes in a small, controlled culture system. It is the combination of small culture units, efficient waste removal through high water turnover, water preparation and storage capacity, multi-phase transfers, and high-performance genetics that makes this model successful. Dividing the culture period into shorter phases (30-40 days) enables greater inventory control, biomass optimization and avoidance of diseases or water quality issues.
Due to the success of this intensive round-tank model, farmers in other countries have expressed interest in bringing this technology to their respective countries. There is no reason why the round-tank intensive culture model could not be introduced as an alternative to the traditional extensive shrimp farms in other shrimp producing countries. Farmers in Thailand, Indonesia and recently, Sri Lanka are already in the early stages of their own round-tank revolution.
(The author is the Founder of Vannamei 101, Hawaii. Views expressed are personal.)
(Please share your experience, interesting news articles and case studies at aquapostnews@gmail.com)