The relevance of using pure oxygen in aquaculture is no longer in doubt. However, around Three-quarters of aquaculture businesses are not yet equipped for this.
But to efficiently metabolise its food intake, a fish must have sufficient oxygen at its disposal, this is not always the case when using traditional aerators. A clear improvement in the conversion index is quite marked with the use of pure oxygen.
In addition, the fish no longer suffer from hypoxia and better defend themselves against bacteria and parasites. A clear decrease is, in fact, recorded in pathological problems and an improvement in the health state of reared stock using pure oxygen.
Even if the use of pure oxygen is not indispensable all the time, the presence of such equipment provides an undeniable security during periods of abundant
stock or simply in the event of an unplanned decrease in natural oxygen present (unforeseen temperature increase, sudden drop in atmospheric pressure, pollution,. ..).
Finally, just as an oxygen can lower conversion rate, better-assimilated foodstuff encourages less waste. For fish farmers anxious to minimise the impact of their installation on the natural milieu, this aspect of using pure oxygen is important.
Factors favouring oxygen transfer
It has been observed in the outline of the main principles that there must be a difference in pressure between the gaseous state and the liquid state if transfer is to occur, just as there must be a certain gas and water flow.
From these principles, three main factors can be determined which will favour the dissolution of oxygen into water: the pressure, exchange surface area, and contact time. It is however difficult to optimise these factors simultaneously. In general, the design of a piece of equipment only aids one of these factors; for example, in U tubes, it is the hydrostatic pressure which is initially focused on. In the case of "above-ground” oxygenators, the pressure is given by the pump and it is then a question of having the closest possible mixing of the water and the oxygen.