The Optical Advantage: Reliable DO Data Improves Aquaculture

The aquaculture industry is growing fast, facing constant pressure to produce more for less. Interest in fish and shrimp is increasing as people around the world recognize seafood as a great source of protein and an essential part of a healthy diet. As demand increases, farmers face a dilemma: how can they produce more product without increasing operational costs?

Increasing density in a pond or tank is one way to meet rising demand and pull in profit. But this delicate business requires close attention to water quality. When so many animals live together, water quality can change quickly, and potentially put the entire stock at risk before farmers are even aware there’s a problem.

Accurate dissolved oxygen (DO) measurements are the first line of defense against loss of stock. Reliable DO data allows farmers to predict when more oxygen is needed and adjust aerators appropriately. Failure to turn on aerators due to poor-quality data could mean the total loss of a harvest, sometimes in less than an hour.

And reliable DO data does more than just protect against death and disease. When farmers have access to accurate DO data, they can increase density without worry, cut costs by running aerators only when necessary, optimize feeding schedules and improve the overall efficiency of their businesses.

“You can’t analyze rubbish data.”

“You can’t analyze rubbish data,” says Alex Hing, In-Situ’s Regional Sales Manager for Asia. Selecting the right technology is crucial to getting an accurate picture of dissolved oxygen levels. Fortunately, advancements in technology have opened up new possibilities for reliable and cost-effective DO monitoring.

While galvanic DO sensors are commonly used for their low initial cost, optical sensors last longer and deliver more reliable data. Comparing the factors below before purchasing a new sensor can help farmers make the best possible investment for their business.

Galvanic DO Sensors	Optical DO Sensors
Requires stirring, warm-up time, hydration, conditioning and special storage	Ready to go right out of the box
Requires frequent recalibration	Holds calibration much longer
Membrane vulnerable to harsh conditions, leading to more frequent damage	Membrane durable and long lasting, leading to lower cost of ownership
Sensor cap needs replacement every six months	Sensor cap needs replacement every year Caps store calibrations for easy, one-step setup
Less accurate at low DO concentrations, requires more sample volume for readings	More accurate at low DO concentrations and with lower sample volumes, leading to more accurate readings overall
Can be affected by sulfides, sulfates, carbon dioxide, ammonia, pH or chloride	Unaffected by sulfides, sulfates, carbon dioxide, ammonia, pH or chloride
Requires continual flow of liquid across the sensor face for accurate readings	Does not require continual flow of liquid across the sensor face, increasing the range of environments in which sensors can reliably operate

Given these differences, optical sensors are worth the investment. The more preparation and maintenance a sensor requires, the more likely it is that some error or inconsistency will skew the data. Hydrating and conditioning galvanic sensors not only takes more time for staff, but also means data could be inaccurate if setup instructions aren’t followed exactly.

And these sensors take extra time and attention even in the water. Galvanic sensor data could be skewed by concentrations of other parameters, flow or abrasive contact, and they won’t read accurately in low sample volumes. Plus, they require more frequent replacement.

Contrast that with optical sensors, which require no preparation, hold up better in harsh conditions and last longer overall. Optical sensors are the clear choice for the long-term health of both your animals and your budget.

“If we can measure, we can predict.”

Dr. Giana Bastos Gomes, now Head of Marine Biotechnology at Temasek Life Sciences Laboratory in Singapore, collected continuous water quality data for her PhD research at City University of Hong Kong. Continuous data allowed her to catch changes in water quality before fish started showing signs of disease.

In one study, she installed an Aqua TROLL in the open pens and ponds of participating farmers. “With this equipment, I can trust that data is always being collected,” she says. “The cost comparison was favorable, especially given the amount of data we’re getting; the installation was straightforward; and the company representatives were very helpful in getting everything set up.”

She adds that continuous monitoring allowed her to alert farmers when there was a change in their water quality. “If we can measure, we can predict,” Dr. Gomes says, “Then we can be proactive. Even a small improvement in mortality numbers can make a big difference to farmers.”

Better Data, Better Business

Reliable dissolved oxygen measurements are essential for farmers who want to take advantage of an expanding market. Accurate data means farmers can make more informed decisions when managing the health of their operation and be strategic in growing their businesses.

Alex Hing says this is the biggest benefit to the accurate data and reliable performance of In-Situ equipment. “If you have easy access to accurate DO measurements,” he says, “You can increase the efficiency of your design. When you have confidence in your data, you can increase your density and not worry it will harm your fish.”