In Fish Production, Water Quality is Vital

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By Milthon Lujan

By Will Hehemann | School of Agriculture, Fisheries and Human Sciences*
During National Water Quality Month, Americans can take some time to consider the importance of clean water in the production of fish found in supermarkets and restaurants across the country, Dr. Amit Kumar Sinha, associate professor of water quality for the Aquaculture/Fisheries Center of Excellence at the University of Arkansas at Pine Bluff (UAPB), said. Water quality plays a crucial role in determining the growth, welfare and health of fish grown in aquaculture systems.


“Fish carry out all their activities in water including breathing, feeding, growth, reproduction, ion balance and excretion,” he said. “The success of a commercial aquaculture enterprise depends on providing an optimum environment to cultured fish.”

Producers who raise fish in aquaculture systems deal with a range of complex water quality parameters that often require continuous monitoring. These variables include temperature, pH, dissolved oxygen, suspended solids, turbidity, ammonia, nitrite, nutrient load, carbon dioxide and other gases, alkalinity, hardness, salinity and metals.

Dr. Sinha’s research at UAPB addresses water quality, aquaculture and fish toxicology and determining ways to increase the production of fish raised for human consumption. Recently, he has been studying the effect of elevated hardness on different fish species.

“Hardness is an integral water quality parameter that can determine the success or failure of an aquaculture endeavor,” he said. “Proper water hardness is required for bone development, blood coagulation, enzyme activity, eggshell integrity and embryonic development of fish.”


Dr. Sinha said hardness is the sum of the concentrations of calcium and magnesium in water. The type of water supply and bottom soil type largely determine the total hardness of water in ponds. Additionally, liming operations could also be a potential source of hardness in fish culture units.

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“As it related to water hardness, the optimal requirements of fish are often species-specific,” he said. “Most fish species perform well over a wide range of hardness values but may suffer when hardness values are too low or too high.”

Hardness below a certain level can be stressful to fish due to relatively low mineral availability. However, greater water hardness can be possibly lethal to fish due to excessive calcium accumulation in vital organs.

“In Arkansas and other southern states, fish producers encounter significant changes in total hardness due to water evaporation during summer months or the dilution of pond water during periods of high precipitation,” Dr. Sinha said. “These events can affect overall fish productivity.”


Producers can adjust hardness in water with the addition of several calcium-based compounds such as calcium chloride, calcium carbonate and calcium sulfate. Calcium chloride is widely preferred because it is highly soluble and also supplements chloride, which is an important ion for fish ion-regulation.

“There is a general consensus that increasing water hardness could help protect fish against salinity shock, heavy metal toxicity, ammonia spikes and pH changes,” Dr. Sinha said. “Considering the benefits of elevated hardness, fish farmers often increase water hardness of culture systems. However, hardness load above the optimal level can incite a toxic effect in fish – these negative effects are often species-specific.”

Specifically, Dr. Sinha is researching the effect of elevated water hardness on commercially important fish species such as channel catfish.

“I am studying a range of biochemical, hematological, calcium homeostasis, iono-regulatory and histopathological parameters to understand the harmful effect of elevated hardness levels,” he said. “Overall, this research will provide a guideline for the ‘maximum level’ of hardness that farmers could maintain in their aquaculture systems.”

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Dr. Sinha’s research at UAPB addresses issues related to improving the fish farming industry and guaranteeing the quality of fish available to consumers. His primary research projects have dealt with ammonia toxicity and stress mitigation in fish and managing harmful algal blooms in aquaculture ponds. He also investigates the impact of pollutants (metals, algaecides and pesticides) on the environment and works to establish better methods to protect aquatic environments.

He has written over 150 publications, including over 70 refereed journal articles and reviews and six book chapters. For more information on water hardness or other water quality issues related to fish production, contact Dr. Sinha at (870) 575-8136 or

Source: UAPN News

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