Round Tank Farm

The Concept of the Super Intensive, Round-Tank Model from Vietnam

I.           Introduction and rationale of the round-tank, intensive culture model from Vietnam

The “round-tank” revolution began approximately 5 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.  However, through relentless trial and error and refining of construction techniques, the advantages of growing shrimp in large above-ground tanks with center drains was realized. 

Today, the development and popularity of this 4th generation, multi-phase intensive farming model in Vietnam has spawned numerous factories producing the construction materials to assemble above-ground round-tanks of various sizes.  This round-tank culture concept is now beyond the research and development phase and is being applied at both the backyard and corporate farming levels. 

II.               Advantages of round-tank culture systems

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 below list highlights the primary advantages of the above-ground, round-tank, multi-phase, intensive culture model:

1. Less initial investment (than intensive lined ponds)

2. High productivity and large shrimp sizes in a small footprint

3. Efficient energy use to circulate water

4. Use existing traditional ponds as reservoirs (recirculation option)

5. Multi-phase system; more harvests per year 

6. More control, less disease risk, more predictable production

Other advantages of the round-tank model include shading of the culture water and ease of transfer to facilitate multi-phase grow-out options.  As a small culture unit has a small footprint, it is easier to cover the tanks with shade netting material for algae control.  Preventing algal dominance results in more stable water quality and less Vibrio bacteria problems.   

III.               Multi-Phase Management Optimizes Efficiency

Many round-tank farmers operate a 3-phase grow-out cycle where the shrimp would be transferred after 30 days (from Phase 1) and again at around 60 days of culture (from Phase 2).  Final harvest size in this 3-phase grow-out cycle would be in the 25 to 40-gram range, depending on market prices.  Easy access to netting the shrimp allows for multi-phase transfers which optimizes the shrimp biomass to water volume ratio.  A two or three phase grow-out cycle provides 3 to 5 harvests per year with shorter grow-out periods per phase. 

The nursery to grow-out tank area is approximately 1:4.  The grow-out tank can serve as the second, third and fourth phase of grow-out by simply splitting the estimated population in half into another grow-out tank.  The more grow-out phases, the shorter the final grow-out phase would be, resulting in more harvest cycles per year.  It is not uncommon to have up to 4 or 5 harvest cycles per year from the same grow-out tank. The most typical size of nursery and grow-out tanks used in Vietnam are 100 m2 and 500 m2 round tanks, respectively.  However, some farms are experimenting with round tanks in the 800 to 1,000 m2 range.

IV.               High Performance Genetics and Post-Larvae Quality

Possibly the most significant driver to the “round-tank revolution” was the contribution of “fast-growth genetics” from imported certified Specific Pathogen Free (SPF) P. vannamei broodstock.  Securing a steady supply of disease-free and healthy post-larvae is paramount for the financial success of this intensive round-tank farming model. 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.

Farmers operating a 4-phase program can achieve 40 to 50 gram shrimp in 130 days at final harvest with high performance genetics. This combination of a controlled, round-tank culture system and shrimp selected for fast growth enabled the round-tank model to become both predictable and profitable.