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Flow-through Aquaculture Systems

In traditional Flow-through Aquaculture Systems, water is passed through the culture system only once and is then discharged back to the aquatic environment. The flow of water through the culture system supplies oxygen to the fish and carries dissolved and suspended wastes out of the system. Water quality within the culture system is maintained by flushing of contaminants and by replacing all system water before dissolved oxygen concentrations drop below minimum acceptable limits or contaminate concentrations (i.e. ammonia, solids, and carbon dioxide) can accumulate to above maximum acceptable limits.

Although flow-through systems are predominantly constructed with raceway culture vessels, more and more facilities are being converted to use circular culture tanks which provide for more efficient use of water, superior mixing, superior removal of solid wastes, and the potential for increased fish densities.

Because flow through systems count on the exchange of water to flush contaminants from the system, high influent flow rates are required and equivalent high effluent flow rates are generated.  Influent treatment and effluent treatment are often required to ensure that water quality is suitable and safe for fish culture or for discharge back to the environment. Because of the high flow rates, extensive treatments are often cost prohibitive and minimal environmental control is possible within the culture system. Temperature control is minimal and is often only possible through the use of systems that recover heat from the effluent flow.

PR Aqua offers a variety of products and services to meet the challenges that face many of today’s flow-through aquaculture facilities. Gas Balancing or oxygenation systems may be used to ensure that dissolved gas concentrations in influent water are appropriate for fish culture. Solids removal and disinfection systems may be used on influent systems to optimize water quality and prevent pathogen ingress, or on effluent systems to mitigate environmental impact. Monitoring equipment which can provide continuous evaluation of key water quality parameters will permit operators to adjust fish densities and feed rates to exactly match the carrying capacity of the culture water.

Flow-through systems became a popular and cost effective approach for aquaculture when water sources were plentiful and competing uses for the water resource were low. However, sustainability principles, increasing competition for limited supplies of high quality water, and the need for improved control of culture conditions are generally causing aquaculture facilities to consider partial reuse or recirculation technologies as alternatives to traditional methods.

Partial Reuse >>>

Flow-through Facts

  • Is a well known culture method that is widely practiced
  • Site placement is limited by water availability
  • Culture systems are relatively simplistic and easy to operate
  • Typically lower capital investment compared to more advanced culture systems
  • Requires high flow rates of high quality water of the appropriate temperature
  • Temperature is fully dependant on intake water conditions
  • Control of temperature and water quality is difficult and usually cost prohibitive
  • Facilities are susceptible to disease ingress with intake water and disinfection of intake water is very costly
  • Produces high volumes of dilute effluent which may be difficult and costly to treat
  • Therapeutic treatments are difficult and inefficient