In the production of fishes in recirculating aquaculture systems oxygen is consumed from the water from respiration of fish and bacteria, as well as from the degradation of organic material. The result is a decrease in the oxygen content of the water which must be replenished, and an equimolar increase in carbon dioxide which must be removed. The most common way of achieving this is by the delivery of air at depth through fine diffusors. This approach was developed several decades ago, and has the advantage that it is a fairly simple installation less prone to mechanical failure and that it can also serve to move water and create circulation. The disadvantage is that it is not particularly efficient at aerating water, it has a risk of generating supersaturated conditions with nitrogen gas, and that it also generates turbulence which is costly for fish to swim in. The purpose of this project is to establish an overview of the mechanical and economical efficiencies of different aeration and degassing methods, through literature studies and practical experiments in order to provide a recommendation for suitable aeration and degassing methods for present day aquaculture purposes, while considering the need to circulate water. The project can be carried out in collaboration with the pump industry.