Aquaculture is the fastest-growing animal-based food industry in the world. Over half of the seafood eaten in the US is farm raised, most being imported. Population growth and diminishing natural harvests put the managed aquaculture industry in a prime position for explosive growth globally. Superior water quality management will be key to ultimate industry success.
Dissolved oxygen (DO) is by far the most important chemical parameter in aquaculture. Low-dissolved oxygen levels are responsible for more fish kills, either directly or indirectly, than all other problems combined. Like humans, fish require oxygen for respiration. The amount of oxygen consumed by the fish is a function of its size, feeding rate, activity level, and temperature. Small fish consume more oxygen than do large fish because of their higher metabolic rate.
Fish farmers, attempting to maximize production, stock greater amounts of fish in a given body of water than found in nature. Frequently, due to increased oxygen demand, it is necessary to supply supplemental aeration to maintain adequate levels of dissolved oxygen.
To obtain good growth, fish must be cultured at optimum levels of dissolved oxygen. A good rule of thumb is to maintain DO levels of at least 5 ppm. Dissolved oxygen levels less than 5 ppm can place undue stress on the fish, and levels less than 2 ppm will result in death. While this is a rule of thumb, warm and cold water species have varying tolerances to low DO levels.
Fish are not the only consumers of oxygen in aquaculture systems; bacteria, phytoplankton, and zooplankton consume large quantities of oxygen as well. Decomposition of organic materials (algae, bacteria, and fish wastes) is the single greatest consumer of oxygen in aquaculture systems. Accordingly, management of supplemental oxygen is critical.
In nature, oxygen enters the water primarily through direct diffusion at the air-water interface and through plant photosynthesis. Direct diffusion is relatively insignificant unless there is considerable wind and wave action. Several forms of mechanical aeration are currently in use to assist nature. The general categories are:
- Vertical sprayers
- Airlift pumps
- Venturi pumps
- Liquid oxygen injection
- Air diffusers
Gaia offers a new, more efficient, and more effective technology for maintenance of DO levels in aquaculture operations utilizing ultra-fine nanobubble generation. None of the above aeration methods generate ultra-fine nanobubbles.
Gaia Oxygenation Technology
There are two components to Gaia’s nanobubble technology that allow it to create DO levels up to 5 times what can be attained through conventional technologies:
- The introduction to water of 97% pure oxygen or 21% oxygen content of ambient air
- The design of Gaia’s ultra-fine nanobubble generating mixing valve>
Because Gaia systems are low pressure, they can be fed with either compressed oxygen in cylinders or through an oxygen generator. Ambient air is fed through an air compressor. While oxygen generators have no ongoing operating costs other than electricity, the efficiency of the technology in its gas use makes compressed oxygen a viable option with low upfront cost.
Ultra-fine nanobubbles have several unique properties including long lifetime in liquid owing to their negatively charged surface, and high gas solubility into the liquid owing to their high internal pressure. Scientific studies in Japan have shown oxygen nanobubbles to significantly increase the dissolved oxygen concentration of water as well as the concentration of the nanobubbles which remain relatively stable for 70 days. Atmospheric air ultra-fine nanobubbles alone (no supplementary oxygen) resulted in an aerial fresh weight increase of over 30% in sweetfish (3 weeks) and rainbow trout (5 weeks). (Ebina K, Shi K, Hirao M, Hashimoto J, Kawato Y, Kaneshiro S, et al. (2013) Oxygen and Air Nanobubble Water Solution Promote the Growth of Plants, Fishes, and Mice. PLoS ONE 8(6): e65339. doi:10.1371/journal.pone.0065339).
Users of Gaia technology are reporting healthy, unstressed, actively feeding fish and significant fresh weight increases at harvest.