Degassing, aeration and oxygenation

Degassing Techniques

Degassing in aquaculture is a process that removes unwanted dissolved gases from the water in fish farming tanks. These gases, such as carbon dioxide (CO₂), nitrogen (N₂), or hydrogen sulfide (H₂S), can be harmful to fish and other aquatic organisms.

Why is degassing important?

• -        Removal of CO₂: Excessive accumulation of CO₂ can lower the water’s pH and affect fish respiration.

•         Reduction of dissolved nitrogen (N₂): Excess nitrogen can cause gas embolism, a problem similar to decompression sickness in divers.

•         Elimination of hydrogen sulfide (H₂S): This toxic gas can be fatal to fish even at low concentrations.

•         Degassing techniques in aquaculture

•         Forced aeration: The use of waterfalls, aeration towers, or air diffusers promotes gas exchange and improves degassing.

•         Gas stripping: Degassing columns force water through materials that facilitate the release of unwanted gases.

•         Forced ventilation: The introduction of high-speed air or partial vacuum in water circuits accelerates the removal of dissolved gases.

• egassing is a crucial step in maintaining good water quality and ensuring the health of fish in aquaculture.

Aeration Techniques

Aeration in aquaculture increases the concentration of dissolved oxygen (O₂) in water. Oxygen is essential for the survival and growth of fish and other aquatic organisms. Aeration also improves water quality by helping to remove harmful gases such as carbon dioxide (CO₂) and ammonia (NH₃).

Why is aeration important?

• -        Oxygen supply: Fish and beneficial bacteria in the biofilter need oxygen to survive and function properly.

•         Elimination of toxic gases: Aeration helps to remove CO₂ and other harmful gases like H₂S (hydrogen sulfide).

•         Improved fish metabolism: Better oxygenation promotes growth and reduces stress in fish.

•         Reduced risk of eutrophication: Proper oxygen circulation prevents excessive nutrient buildup, limiting the proliferation of harmful algae.

Aeration techniques in aquaculture

There are several methods to ensure proper water aeration:

• -        Natural aeration: Using wind and natural water movement (e.g., waterfalls, streams). This simple technique is suitable for open systems such as ponds.

•         Mechanical aerators: Devices that increase oxygen exchange between air and water through agitation or air injection. Examples include:

•         Paddlewheel aerators: Create waves and bubbles to oxygenate water.

•         Jet aerators: Spray water into the air for better oxygen contact.

•         Diffused air aerators: Use pressurized air diffusers to release fine oxygen bubbles into the water.

How to choose the right aeration method?

The choice depends on several factors:

• -        Type of aquaculture system (ponds, tanks, RAS)

•         Fish density (the more fish, the more oxygenation is needed)

•         Cost and energy availability

•         Water parameters (temperature, salinity, etc.)

Proper aeration is essential for maintaining healthy and profitable aquaculture production.

Oxygenation Techniques

Oxygenation in aquaculture is the process of maintaining an optimal level of dissolved oxygen (O₂) in the water to ensure fish health and optimize their growth. It is especially crucial in intensive farming systems where oxygen consumption is high.

Why is oxygenation important?

• -        Fish respiration and aquatic organisms consume oxygen.

•         Low oxygen levels cause stress, reduced appetite, and slower growth.

•         Oxygen deficiency can lead to mass fish mortality and significant growth delays.

•         Nitrifying bacteria that convert ammonia (NH₃) into nitrites (NO₂⁻) and nitrates (NO₃⁻) need oxygen to function.

•         Insufficient oxygenation can lead to toxic waste accumulation.

•         Reduction of diseases and improved metabolism

• -       Good oxygen levels reduce stress and improve fish resistance to diseases.

•         Oxygen promotes digestion and nutrient absorption.

•         Optimal oxygen levels enhance farming performance.

Oxygenation methods in aquaculture

• Injection of pure oxygen (direct oxygenation): Using liquid oxygen (LOX) or oxygen generators. This method is highly effective and is used in high-density systems such as recirculating aquaculture systems (RAS). Oxygen supply can be adjusted based on fish consumption.

• Several systems can enrich water with oxygen, including:

•         Oxygenation cones

•         Jet platforms

•         Low- or medium-pressure oxygen systems

•         Pure oxygen diffusers

•         Use of plants and algae: In extensive systems, aquatic plants and phytoplankton produce oxygen through photosynthesis. However, at night, plant respiration consumes oxygen, which can cause problems.

Factors influencing oxygenation

The level of dissolved oxygen depends on several parameters:

• -        Temperature: Warm water holds less oxygen than cold water.

•         Salinity: Salty water naturally contains less oxygen than freshwater.

•         Fish density: The more fish, the higher the oxygen consumption.

•         Biological activity: Biofilter bacteria and decomposers also consume oxygen.

How to optimize oxygenation?

• Continuously monitor dissolved oxygen levels using oxygen sensors.

•         Adjust aeration and oxygenation based on fish needs.

•         Use aerators or pure oxygen to prevent stress and losses.

•         Avoid overfeeding, which increases oxygen consumption by waste-decomposing bacteria.

Oxygenation is a key factor in maximizing productivity and ensuring a healthy environment for fish.

AQUACULTURE France offers a wide range of services and equipment to meet all the needs of aquaculture partners.