Question

Various methods of aquaculture can be used to grow species of marine fish. Consider the figure below, which shows one way that an aquaculture system can be set up. Explain whether this represents an open or closed system and one benefit of using this type of system.

Answer 1

The system is an open system. It needs to be open to allow air to contact with the water where the fishes are growing. Allowing air to contact means more oxygen is allowed to penetrate into the water and increases the oxygen content allowing more oxygen for the fish to use. In the process, the first step would be adding water into the fish tank, then the water will be mechanically filtrated to remove dirt, dead plants and feces brought by the fish. The filtrated water will then undergo biological filtration to remove pathogens that are not eliminated during mechanical filtration. The dirt form both filtration will go to the waste area and the clean water will be used back to the fish tank.

Answer 2

The system is open.

An open system is one where mass is able to flow in and out of the system. The mass entering this system is the water that is added to the fish tank, and the leaving mass is the waste that is generated.

The primary advantage of using this system is that the quality of the water supplied to the fish may be maintained, meaning the fish are healthy and do not have to live in waste, as they would have to if the system was closed.