Oxygenation in tank culture systems (e.g. RAS and race-ways) is one of the key factors affecting fish growth and welfare, and one of the major important production costs. Recent developments in RAS tank design faced the problem about how to make dissolved oxygen available for the animals in the tank (in-situ), especially in shallow (1.5m) and large surface area, or deep (4-6m) and circular tanks.
The analysis of available oxygenation solutions and potential new oxygen transfer technologies considered relevant aspects such as oxygen input efficiency and dissolved gas distribution over time and space in the tank, as well as energy demand, individuality, and independency.
After a thoroughly analysis, a novel in-situ oxygenation system was developed. It consists of an independent low power consumption unit with a ceramic membrane that operates at both low gas and water pressure. Table I shows the amount of oxygen input level and energy demand of the oxygenation system (named Canox).
As a self-sufficient and plug-and-play device, the unit can be quickly installed and retrofitted into existing tanks. The Canox oxygenation device is installed directly in/at the tank and uses the internal tank circulation and water flow for a very even oxygen distribution, ensuring a good oxygen supply. Due to the low gas and water pressure, there are no generation of harmful pressure release bubbles. Moreover, the normal behaviour of the fish and shrimp were not affected. The unit works completely independent of the main water circulation system and transfers oxygen into the tank even if the main water flow is stopped.
Existing technologies (low head oxygenators, U-tubes, oxygen cones, among others) were found to be inappropriate for an in-situ oxygenation. Other technologies were characterised by an extremely high cost at similar gas input efficiency levels.