Recirculating Aquaculture Systems (RAS) enable land-based control of environmental conditions, including water quality, which directly influences fish health, growth, and productivity. In 2024, Canadian farmed finfish production increased to over 122,000 tonnes, highlighting the growth of the industry and reinforcing the need for effective monitoring practices to maintain sustainable operations. (www150.statcan.gc.ca)

Quality water management is central to successful aquaculture: without it, fish welfare, biosecurity, and economic viability can all be compromised. This guide explains how to monitor water quality in fish farming, the tools you need, key parameters to watch, and best practices for RAS operators.

Why Water Quality Monitoring Matters in Aquaculture

Water quality affects fish metabolism, disease resistance, feed efficiency, and overall survival rates. In RAS, where water is continuously recirculated and reused, monitoring enables operators to:

• Prevent toxic buildup of waste compounds such as ammonia and nitrite.
• Maintain optimal dissolved oxygen and pH levels for fish welfare.
• Ensure regulatory compliance and environmental stewardship.
• Reduce water usage — RAS can use up to 95–99% less water than traditional flow-through systems when properly monitored. (Finnforel)

Water quality monitoring is not just a best practice — it’s essential for sustainable, efficient, and profitable aquaculture.

Core Water Quality Parameters to Monitor

In RAS systems, continuous or routine measurement of the following critical parameters is recommended:

Dissolved Oxygen (DO)Optimal DO levels are essential for fish respiration; target values typically remain above 5 mg/L. (Water Quality Sensors)

pH LevelspH affects the toxicity of nitrogenous compounds and biological activity; maintaining stable pH within species-appropriate ranges supports fish health. 

Ammonia, Nitrite & NitrateAmmonia and nitrite are toxic byproducts of fish excretion and feed breakdown. Regular monitoring allows for timely corrective actions through filtration and biofiltration.

TemperatureTemperature influences metabolic rates and oxygen solubility; precise control ensures conditions suit the cultured species.

Turbidity & Total Suspended SolidsHigh turbidity can stress fish and interfere with filtration efficiency.

Efficient monitoring combines manual testing at scheduled intervals with automated probes and sensors capable of real-time reporting.

Step-by-Step Guide: How to Monitor Water Quality

Below is a practical workflow tailored for RAS facilities:

1. Establish a Monitoring Schedule

Develop a routine based on the production phase and stocking density. Early morning, pre-feed, and end-of-day checks help capture daily variability.

2. Install Sensors and Controllers

Set up reliable water quality probes for DO, pH, temperature, and ammonia. Prefer real-time monitoring systems that integrate with control units.

3. Calibrate and Validate Instruments

Regular calibration with standard solutions ensures accuracy. Verify against handheld meters or lab tests when necessary.

4. Record and Analyze Data

Use data logging software to track trends. Automated alerts can signal deviations before they affect fish welfare.

5. Take Corrective Actions Promptly

If readings exceed acceptable thresholds, implement responses such as:

Increasing aeration.

• Adjusting feed rates.
• Backwashing filters.
• Partial water exchange in emergencies.

6. Maintain Biofilter Performance

Effective biofilters are critical to converting ammonia into less harmful nitrate. Monitor biofilter health through water chemistry and flow rates.

Tools and Equipment for Effective Monitoring

To monitor water quality effectively in RAS, you’ll want:

• Multi-parameter sensors (DO, pH, temperature)
• Ion-selective probes for ammonia and nitrite
• Data loggers & automated alert systems
• Handheld portable meters for onsite verification
• Filtration systems, including drum filters and biofilters

Investing in quality instruments and redundancy systems reduces risk and safeguards production continuity.

Best Practices for Water Quality Monitoring

To optimize outcomes:

• Implement a data-driven management plan. Automated logging enhances trend analysis and decision-making.
• Adopt redundancy for safety. Duplication of critical sensors prevents blind spots.
• Train staff in routine procedures. Consistent sampling and interpretation minimize mistakes.
• Schedule preventive maintenance. Cleaning sensors and replacing worn parts improves long-term performance.
• Evaluate and adjust feeding practices. Overfeeding contributes to waste accumulation that degrades water quality.

Conclusion

Monitoring water quality in aquaculture — especially in Recirculating Aquaculture Systems — is not optional: it’s a cornerstone of modern, responsible fish farming. By following a structured approach, equipping your facility with reliable tools, and implementing best practices, RAS operators can maintain optimal water quality, improve productivity, and uphold environmental stewardship.

OceanStar Technologies supports Canada’s aquaculture innovation with smart solutions that help producers thrive in a competitive and sustainable marketplace.