From Chore List to Design Philosophy
In many operations, biosecurity is approached as not much more than a checklist of chores: dip your boots, clean your nets, and hope for the best. While these tasks are important, biosecurity is more effective when treated not as a response to disease outbreaks but as a built-in design philosophy that keeps things running smoothly from the outset. The goal is to create an environment designed from the ground up to prevent, detect, and contain pathogens— a “defensible space,” so to speak.
A well-designed, lined tank provides the physical foundation for this environment. However, hardware is only half the equation. Physical control should be paired with a rigorous operational plan to provide dependable protection. This chapter details how to create that plan and how to leverage the liner as the first line of defense.
Your First Line of Defense
Your first line of defense in a hatchery tank is the surface that shields the water and your fish from external contaminants. While common construction materials like concrete seem solid and inert, they can present a hidden biosecurity risk.
On a microscopic level, unsealed concrete is a porous material, full of tiny crevices. Crevices can harbor bacteria, fungi, and other pathogens and shield them from disinfectants. This makes it exceptionally challenging to achieve a sterile environment between cycles, as lingering pathogens can remain hidden within the tank walls themselves.
An impermeable geomembrane liner solves this problem by creating a smooth, non-porous barrier over the structural tank material, which eliminates any hiding places for pathogens. Because the surface is completely sealed, disinfectants can fully activate over the entire surface for a complete “hard reset” and a reliably sterile environment for each new batch of alevin.
Thinking Like a Pro: An HACCP Approach
Professionals in the food industry use a system called HACCP (Hazard Analysis and Critical Control Points) to manage safety. It’s a helpful mindset that shifts the operational focus from reacting to contamination to preventing it from ever happening. The same professional approach can be very effective when applied to hatchery biosecurity.
An HACCP approach depends on identifying all potential biosecurity hazards. These hazards fall into two categories: pathways for new pathogens to enter your system, and opportunities for existing pathogens to persist between cycles. External pathways include the incoming water source or staff and equipment moving between tanks. However, one of the most significant internal hazards—and the one most often overlooked—is the structural surface of the tank itself.
A “Critical Control Point” is any step where a control can be applied to prevent or eliminate a hazard. A high-performance geomembrane liner acts as a permanent, built-in CCP. By establishing a smooth, non-porous, and sterilizable surface over a material like concrete, the liner eliminates the hazards of a contaminated tank wall. Pathogens are easily removed during cleaning, and they have no place to hide from disinfectants. Liners are an essential element that makes all subsequent biosecurity measures, like water disinfection and cleaning protocols, significantly more effective.
The Ultimate Weapon: A “Hard Reset”
The most powerful biosecurity practice in modern aquaculture (including hatcheries) is the “hard reset” performed between production cycles. This is a standard, multi-step protocol designed to break disease life cycles by eliminating pathogens left over from the previous batch. Its effectiveness, however, depends entirely on the quality of the tank’s surface.
A hard reset begins with completely draining the tank and physically removing all accumulated organic sludge. This is followed by a drying period, sometimes called “fallowing.” Exposing the surface to desiccation and sunlight (UV radiation) is a low-cost and highly effective way to kill many waterborne pathogens and pests, including their hardy resting stages. As a final step, disinfectants can be applied to the clean, dry surface to neutralize any remaining threats.
A non-porous tank surface, such as a geomembrane liner, makes this entire process uniquely effective. Sludge can be removed completely, leaving no waste embedded in the surface. A liner dries quickly and thoroughly, unlike porous concrete or soil, which can retain moisture and shield pathogens deep within their structure. Finally, the smooth surface ensures disinfectants can achieve full, even coverage. The improved effectiveness of the hard reset is a fundamental advantage of lined systems, allowing each new batch of alevin to get their start in a reliably sterile environment. This has a measurable impact on biosecurity. One 2022 study, for example, found that lined shrimp ponds had a 34 times lower total bacterial count and a 25% lower pathogenic Vibrio load than comparable earthen ponds, a direct result of effective sludge removal and sanitation.
Smart Layouts for Clean Operations
Effective biosecurity practices go beyond individual tanks to the overall facility design. A smart layout is designed to manage workflow and control traffic, improving efficiency while minimizing the risk of cross-contamination between different areas of the hatchery.
To prevent cross-contamination, distinct zones are established for different operational purposes and for managing the movement of people and equipment between them. For example, a dedicated quarantine area for new or sick animals should be physically separate from the main production area.
The layout should also establish "clean" versus "dirty" pathways. This ensures that staff and equipment do not move from a potentially contaminated area to a clean one without passing through a control point, such as a footbath or a disinfection station. A well-planned layout reinforces biosecure protocols, ensuring they’re an integrated part of the daily workflow rather than an afterthought.
A Note From the Trenches
A simple and effective way to maintain biosecurity between separate production areas is by using color and pattern coding. Start by assigning each zone a specific color and pattern: solid red for the quarantine area, for example. Mark all equipment used in this area (nets, buckets, and brushes) accordingly.
Green stripes may apply to the main production area and would be allotted their own color-coded tools, while a crosshatched blue design could designate the broodstock area. This creates a clear, visual reminder that is easy for all staff to follow. If a health issue is detected within a specific tank, it can be immediately flagged as a temporary “contaminated” zone - perhaps by erecting a bright orange sign with a warning symbol - and placing its own set of isolated equipment nearby.
This same philosophy can be applied to foot traffic by using colored epoxy coatings or painted lines on the floor. A red line marking the boundary of the quarantine zone provides an unmistakable visual cue so no one passes without disinfecting. It’s a low-tech solution that dramatically reduces the risk of accidental cross-contamination from both equipment and staff.
Looking Ahead
With a biosecure facility and smart operational protocols in place, you’ve created a stronghold against disease. But an empty tank won’t meet your mission objectives. The next step is to transform your sterile containers into a vibrant, life-sustaining aquatic environment. This requires understanding the nuances of water chemistry and how to manage them within the controlled, inert world of a lined tank.
In the next chapter, we’ll consider the chemistry of control, from mastering the nitrogen cycle to managing quality parameters for a stable, healthy environment for your stock.
