Tilapia is a popular food fish that has been pond farmed for thousands of years. We do for instance know that the Ancient Egyptians farmed tilapias along the Nile. Today, traditional pond farming has been accompanied by tank farming and cage farming. Pond raising, tank raising and cage raising all come with their respective advantages and disadvantages that must be carefully assessed by the prospective tilapia farmer.

Cage culturing makes it possible to grow tilapia in bodies of water where draining and seining would be difficult or impossible. Cages are for instance utilized in lakes, large reservoirs and rivers. They are also a good alternative for estuaries and coastal embayments, and have been successfully used for farming tilapia in cooling water discharge canals. The cages consist of mesh in order to let the water circulate freely.  

Generally speaking, large bodies of water are more suitable for cages than small ones, since the water quality is less stable in small bodies of water and more easily affected by the waste produced by the fish. If you want to cage culture tilapia in a small body of water (<5 acres / <2 hectares), the safest course of action is to make emergency aeration available and/or carry out water changes.

Choosing species

A few examples of tilapia species and variants commonly grown in cages are Nile tilapia (Oreochromis niloticus), Blue tilapia (Oreochromis aureus ) and the manmade variants Florida Red and Taiwan Red. The perfect species or hybrid for a particular fish farm will depend on several factors, such as availability, growth rate and cold tolerance. It is important to keep in mind that many species and hybrids are prohibited in certain parts of the world. Nile tilapia is a fast grower, but it is prohibited in many regions outside its native range. It is also less cold tolerant than Blue tilapia, which is a popular choice among fish farmers outside the tropics. Florida Red and Taiwan Red are appreciated for their fast growing rate and reddish coloration.  

Recent research has shown that it is possible to grow Florida Red tilapia in cages placed in sea water. It is however very important to slowly adjust the fingerlings to marine conditions over the course of several days. The fish will also be more prone to ill health since the high salinity makes it less strong. You should also be aware that marine water contains a whole new set of potentially malicious micro organisms. It will on the other hand kill many pathogens adapted to freshwater conditions. You must naturally use materials known to be durable in marine conditions when you build your cages, otherwise they will rapidly corrode. There is also a risk of so called marine biofouling, i.e. the undesirable accumulation of marine micro organisms, plants and animals on submerged objects.

Advantages and disadvantages of cages compared to ponds and tanks

Advantages

• Feeding and harvesting is typically less labour intensive in tanks than in ponds.
• In ponds where both male and female tilapias are grown, a high number of offspring can be produced in no time and the offspring can harm fish production by competing with the adult fish for food. When tilapia is farmed in high density cages, the breeding cycle of tilapia is disrupted. The eggs will normally fall through the mesh before they are fertilized and eggs that do get fertilized will usually fail to develop into fry. It is however important to keep in mind that a cage made from 1/10-inch mesh or smaller will be able to retain eggs. 

Disadvantages

• Pond grown tilapia can make use of naturally occurring food, while cage grown tilapias only have a limited access natural food since they cannot forage on their own. Cage grown tilapia therefore needs to be fed by you to a much higher extent. The food that you give your cage grown tilapia also has to be complete, e.g. contain proper amounts of all necessary vitamins and minerals.
• When tilapia is grown in cages instead of ponds, most farmers opt for a high stocking density. A high stocking density creates a stressful environment for the fish and stress damages the immune system. The risk of disease is therefore high. The risks will be increased further if the farmer fails to provide the fish with optimal water conditions and a satisfactory diet.
• The legal status for tilapia cages placed in public waters is unclear in many parts of the world.
• Predators can be attracted to the cages and engage in poaching.
• Storms can damage the cages.

Placing cages

• Tilapia cages should ideally be placed where the water currents are greatest, but rough water with really strong currents should be avoided.
• Placing tilapia cages in stagnant water is not advisable. 
• To increase the chances of high water quality, the cages should ideally be placed at least 4.5 meters (15 feet) from each other.
• Do not place cages closer to the bottom than 90 cm (3 feet). An even greater distance is recommended, since it will reduce the risk of disease and promote a more rapid growth rate. 
• Both floating cages and standing surface cages can be used. Cages can be individually moored or linked together. You can for instance suspend ropes across the surface and attach the cages to them. Using piers and rafts is also popular.

Temperature

The recommended water temperature for tilapia is 28-30 degrees C (82-86 degrees F) since this is the interval where optimal yields can be acchieved. The growth rate will decrease if the temperature goes any lower, and it will start declining dramatically if the water is colder than 20 degrees C (50 degrees F). Tilapia will normally start dying at roughly 10 degrees C (50 degrees F). It is also important to keep in mind that a temperature below the recommended range will have a negative impact on the immune system of the fish. Your fish might survive at first, but it will be highly susceptible to possibly fatal attacks from bacteria, viruses and parasites. A water temperature below 13 degrees C (55 degrees F) is never advisable.