Oxygen generator for fish farming

- Jul 22, 2016-

Oxygen generator fish farming

If you’re in the aquaculture industry, you’re very familiar with the benefits of O2 — for fish growth, health, and 

maximizing population density.

Lower cost than traditional liquid oxygen, skid mounted and easy to move, small mainten

It aquires oxygen by separating oxygen directly from the atmosphere and deliver it to  application with an oxygen generator. Only electricity is consumed, without material consumption.

Oxygen generator for farm fish


Fish farming

Fish farming is the principal form of aquaculture, while other methods may fall under mariculture.

It involves raising fish commercially in tanks or enclosures, usually for food.

A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish hatchery.

Fish species raised by fish farms include salmon, catfish, tilapia, cod and others.

Basically, there are two kinds of aquaculture: extensive aquaculture based on local photosynthetical production and intensive aquaculture, in which the fishes are fed with external food supply.


Demand is increasing for fish and fish protein, which has resulted in widespread overfishing in wild fisheries. China provides 62 percent of the world's farmed fish. As of 2016, more than 50% of seafood was produced by aquaculture.

Farming carnivorous fish, such as salmon, does not always reduce pressure on wild fisheries, since carnivorous farmed fish are usually fed fishmeal and fish oil extracted from wild forage fish. The 2008 global returns for fish farming recorded by the FAO totaled 33.8 million tonnes worth about $US 60 billion.


Fishes are a kind of cold-blooded vertebrates living in water all their life, breathing through gill and utilizing the dissolved oxygen from the water, moving and keeping balance in the water by their appropriate fins.

It is impossible for fish surviving without water, because of the natural surroundings, water effects fish generation after generation, they have their own peculiar types of body and some organ to adapt water environment.

They breathe oxygen in the water by gill. It would be impossible for fish to survive without water because of their nature. Water affects fish one generation after another. They have their own peculiar (special) body types and organs in order to adapt water environment. The gills absorb oxygen from the water and release carbon dioxide from the respiration system through those tiny capillaries in the gill filaments.


Key factors

(a) The water temperature should be around 18-28℃.

(b) The pH should be around 7.0-8.5.

(c) Dissolved oxygen should be adequate.

(d) The water should be clean (without harmful ions Pb2+, Hg+), and without harmful zooplankton.

Key technologies

(a) Select parent-fish when they are in good matured status.

(b) Use correct hormone, and the dosage according to the different species with a high temperature being low dosage.

(c) Distinguish if the eggs have reached matured stage (matured eggs should appear separate from each other).

(d) Good management in all hatching procedures.

Growth of Fish

Growth can be defined as: the change in size (length, weight) overtime or energetically, as the change in calories stored as somatic and reproductive tissue. Factors affecting growth of fish are followings.

Age and maturity

Age and maturity are usually the best predictors of relative growth rates in fishes, although the absolute growth rates are strongly influenced by environmental factors. Thus fish typically, growth very rapidly in length in the first few month or years of life, until maturation. Then increasing amounts of energy are diverted from growth of somatic tissues to growth of gonad tissues. As a consequence, growth rates of mature fish are much slower than those of immature fish.


Temperature is among the most important environments variables.  For example growth in desert pupfish increases with temperature up to 30 degree Celsius. Maximum growth rates of salmon are achieved at intermediate temperature (15%). Generally fish tend to prefer temp at which their growth is maximum.

Food availability and quality

Food availability and quality affects growth by interacting with other factors, particularly temperature. In some species of fish growth is accelerated during warmer months of plentiful food. Compensatory growth occurs after feeding is temporarily stopped, and growth accelerates when feeding is resumed. Regarding to food quality, a complete diet (with amino acids, fatty acids and vitamins) is required for high growth rates in fish.


Different fish species has different growth rates and growth patterns.


Adaptability and tolerance of fish to physical and chemical qualities of water

The different species of fish has a different adaptability and tolerance to physical and chemical qualities of water.

1 Temperature

The range of temperature prevailing in pond water imposes a definite limitation upon the choice of fish to be cultivated, because different fish have different ranges of temperature-tolerance. Also the reproduction, growth, and the breathing rates of fish are directly dependent upon temperature variations.  For warm water fishes, the suitable water temperature is usually from 16 to 35.  The preferred water temperature range is between 22℃ and 32℃. When the water temperature is below 16℃ or above 35℃, feeding rate will decrease and the growth will be affected. When the water temperature is above 38℃, feeding stops and fish will die gradually.  Tropic fishes, such as Nile tilapia, can tolerant higher water temperature but cant tolerant lower water temperature.  When the water temperature is below 10℃, the fish will die (Figure 1-18).  The lethal low temperature is between 10 and 13℃.  The lethal high temperature is between 40 and 42℃, and the death high water temperature is above 42℃.

The lower water temperature is suitable for coldwater fishes.  Rainbow trout grows well when the water temperature is below 18℃.  When the water temperature exceeds 20℃, the growth will stop and fish will die.

2 Turbidity or transparency

The turbidity, expressed as transparency, is an important factor, no matter what are the causes. Turbidity, when it is due to plankton growth, is a good sign. However, when it is due to suspension of silt and/or clay particles, turbidity may be harmful to many fishes cultured. Some fishes could adapt to live in such waters and others can tolerate a certain range of turbidity.  Different species of fish needs different transparency.  The lower transparency caused by plankton is suitable for filtering fishes, such as silver carp and bighead carp, and omnivorous fishes, such as tilapia.  The preferred transparency is from 25 to 30cm for filtering fishes and omnivorous fishes.  Carnivorous and herbivorous fishes like the clear water with high transparency.

3 Dissolved oxygen

The adaptability of fish to dissolved oxygen content is above 5 mg/L.  Nile tilapia can tolerant 0.1 mg/L of dissolved oxygen content several hours.  Carnivorous fishes will die when the dissolved oxygen content fell down to 0.5 mg/L.  3 mg/L of dissolved oxygen content will be dangerous for Nile perch.

4 pH

Fish can grow well when pH value is between 6.5 and 9.0, and the preferred pH value is between 7.0 and 8.5. The tolerance of fish to high pH is 9.5 and low pH is 4.0.  But tilapia can survive several days when pH rise to 10.

5 Ammonia

Most of fish excrete their nitrogenous waste in form of ammonia, which can accumulate in intensively managed ponds to levels as high as 1-2 mg/L.  The long term exposure to un-ionized ammonia reduces fish growth.  The hyperplasia of epithelial tissue of gill will occur.  The adaptability of fish to ammonia is lower 0.1 mg/L. Ammonia ionizes in water and the proportion of the un-ionized form (NH3) in an ammonia solution increases with pH and water temperature.  Fractions of NH3 in an ammonia solution at various pH and temperature values are showed in Table below.


Dissolved oxygen (DO)

One major characteristic of water quality that is important to the growth and survival of fish is dissolved oxygen.  Oxygen consumption by fish and dissolved oxygen requirements increase with temperature and feed consumption.  As intensification increases, dissolved oxygen can often become a limiting factor.  While tilapia is generally tolerant of low dissolved oxygen, extended periods of hypoxia may cause reduced growth and increased mortality, particularly when algal blooms occur.  Many fish have shown reduced growth or survival when dissolved oxygen condition fall below levels as high as 5mg/L, or 25 to 50%saturation.  However, there appear to be no guidelines as to what level of dissolved oxygen causes reductions in growth of tilapia.  Dissolved oxygen can be tested with chemical method (titration with Na2S2O3 dropper). Different species of fish have different lethal dissolved oxygen.


Lethal D.O of different species of fish

  Species of fish

Lethal D.O. (mg/l)


Lethal D.O. (mg/l)

  Common carp




  Silver carp


Butter fish


  Bream grass carp


Rainbow trout





Generally, fish of bottom inhabiting requires lower dissolved oxygen; fish of surface or middle niche requires higher dissolved oxygen; fry and fingerlings require the highest dissolved oxygen. Culturist can increase dissolved oxygen by aerator or adding fresh water into pond.