Water Quality and Ozone Applications in Fish Farms

Introduction

Turkey ranks among Europe's largest aquaculture producers. Tens of thousands of tonnes of sea bass, sea bream, and trout are produced annually along the Aegean and Mediterranean coasts. At this scale, water quality is no longer a matter of preference — it is a direct question of profitability and sustainability.

In traditional open-cage systems, water quality was largely left to natural currents. But as production intensifies, disease pressure increases, environmental regulations tighten, and recirculating aquaculture systems (RAS) become more widespread, water quality management has become a critical engineering discipline.

Ozone is at the centre of this transformation.

Key Water Quality Parameters in Fish Farms

Water quality management directly determines fish health, growth rate, and product quality.

Dissolved Oxygen: The fundamental parameter for fish respiration. Stress begins below 6 mg/L; mass mortality risk rises below 4 mg/L. Ozone systems operating alongside oxygen generators maintain this level continuously at optimum.

Ammonia (TAN): The primary metabolic waste product of fish. At high pH and temperature, the proportion of toxic free ammonia increases. Ozone oxidises ammonia, reducing the load on biological treatment.

Nitrite: An intermediate product of the biological treatment process. Even low concentrations cause methaemoglobinaemia. Ozone supports nitrite oxidation.

Suspended Solids (SS): Feed residue, faeces, and dead organic matter. Causes gill damage, pathogen proliferation, and increased oxygen consumption. Ozone breaks down organic matter, reducing SS accumulation.

Pathogen Load: Bacteria, viruses, and parasites. As production density rises, so does pathogen pressure. Ozone offers substantially greater efficacy than chlorine in this area.

How Ozone Improves These Parameters

Ozone (O₃), through its powerful oxidation properties, improves multiple water quality parameters simultaneously.

Pathogen Control

Ozone provides broad-spectrum disinfection against bacteria, viruses, fungi, and parasites — approximately 3,000 times more powerful than chlorine. It has proven efficacy against Vibrio, Aeromonas, and white spot disease (Ichthyophthirius), among the most significant pathogen challenges in aquaculture. This enables a substantial reduction in antibiotic use — a critical advantage both for cost and export quality.

Organic Load and Colour Removal

Ozone oxidises and breaks down organic matter in water. The water clarifies, oxygen consumption decreases, and nutrient sources for pathogens are eliminated. In intensive production facilities, water gradually yellows and produces odour — ozone rapidly eliminates these compounds.

Biofilm Control

Biofilm forming on tank walls and pipe surfaces provides shelter for pathogens. Ozone penetrates biofilm and destroys colonies that chlorine cannot reach.

The Role of Ozone in RAS Systems

In recirculating aquaculture systems, water is continuously recycled. Contaminants accumulate and can rapidly reach toxic levels. Ozone intervenes at four critical points in these systems:

Before the biofilter: By reducing ammonia and nitrite loads, it relieves pressure on the biofilter. The biofilter operates more efficiently and requires less space.

After the microscreen filter: Following suspended solids removal, ozone oxidises remaining pathogens and organic matter.

Before UV disinfection: Ozone enhances the efficacy of UV disinfection. The combination achieves significantly higher pathogen removal than UV alone.

Discharge water treatment: Before RAS effluent is released to the environment, ozone provides final treatment to meet regulatory standards.

Ozone + Oxygen Generator Combination

In aquaculture applications, ozone generators always operate in conjunction with oxygen generators.

There are two reasons for this: First, ozone generators fed with pure oxygen produce 2–3 times more ozone than air-fed systems for the same energy consumption — substantially higher efficiency. Second, RAS systems already require an oxygen generator to maintain dissolved oxygen levels. The same oxygen source can serve both ozone production and direct aeration — saving both space and energy.

At OCS Ozon, we design integrated ozone and oxygen generator systems for aquaculture projects. One supplier, one point of responsibility.

Key Considerations

Residual ozone control is essential. Water reaching the fish must contain no residual ozone. In RAS systems, an activated carbon filter or UV destruction unit is installed at the ozone reactor outlet.

Dose control is critical. Ozone dose must be precisely adjusted to target water quality parameters, using sensor-based automation.

Gas-phase ozone must be monitored. An ambient ozone sensor should be installed for facility air quality, with an alarm system triggered if OHS limits are exceeded.

Conclusion

Water quality management is one of the most critical competitive parameters in modern aquaculture. Ozone technology delivers significantly more effective and sustainable results than conventional methods in pathogen control, organic load removal, and oxygen transfer.

Turkey's large fish production facilities should treat this technology as a strategic tool for achieving growth and export targets.

OCS Ozon designs site-specific ozone + oxygen integration systems for aquaculture facilities. Contact us for a free technical assessment.