3. Tilapia Recirculated Aquaculture Systems (RAS)

So with the species chosen the technique of producing them as optimally as possible becomes important. This is the How part of the discussion – How do we produce the fish consistently and predictably?

There are several techniques available to the fish farmer.

  • Cage farming
  • Pond farming
  • Raceway/flow through farming
  • Recirculated Aquaculture Systems (RAS) farming
  • Hybrids of some of these systems

Cage farming is currently one of the most popular method of producing tilapia. It has constraints of location – given that tilapia grow optimally at 28C water there are limited bodies of water of sufficient size and year round temperature that are suitable. Very large lakes and dams are used extensively in the East and Central America where the climate is conducive. In Africa some operations manage to produce tilapia using cages.

Cage farming is relatively labour intensive, expensive to maintain, risky from a disease and water quality point of view but other than feed has no constraints in terms of water management. The lack of control over the water environment is offset by the lack of cost associated to control it. However risks of predation, theft, disease, climate and environmental factors beyond the control of the farmer need to be adequately quantified.

High stocking densities can be achieved. Environmental impacts and long term effects of high intensity localised fish production are not yet fully understood. The ability to scale operations is determined by the available water space.


Pond farming on the other hand relies on building out large relatively shallow (2m depth max) earth ponds, typically several thousand square metres each. These ponds are lightly stocked and can yield between 10 and 15 tons per hectare depending on climate and utilisation. Labour usage is low, relegated mostly to feeding and harvesting of the ponds. The ability to scale is limited by the land space available and the supply of water to fill the ponds. Risk is relative – the farmer has no control over the environment, theft and predation pose risks and it is only at harvest time that the farmer is able to accurately assess his production. Disease control however is relatively robust. Scaling operations becomes challenging owing to the sheer size of land space required.


Raceway or flow through systems have limited locations. These, as the name implies, require large quantities of fresh water that can be continually flown through a series of tanks in which fish are located. Costs are low unless the water has to be pumped. No filtration is required and risks are the usual ones of environmental influence, water quality of the source and possible disease introductions. However high stocking densities can be attained and scaling of operations is limited by the quantity of water available. Labour usage is relatively low.


RAS systems are substantially more expensive and high technology than other production systems but in turn free up their location to anywhere there is sufficient water and reliable power. RAS uses very little water per kg of fish produced, orders of magnitude less than the other production techniques owing to the ongoing circulation and filtration of the water to free it from the wastes produced by the fish. RAS affords fish farmers almost total control over the production environment, allowing for predictable production. Any of the important production parameters can be manipulated within a RAS environment and very high stocking densities can be attained. RAS uses a relatively small foot print as a result and has less environmental impact than other production techniques. RAS is relatively light on labour demands but is high on management demands.


It is our opinion that the nile tilapia is the only commercially viable species that can be successfully farmed. As a result of this opinion RAS is the only system that can produce nile tilapia predictably and consistently enough in order to ensure success on a commercial basis. Further, our view is continuously reinforced by the ongoing development of land based fish farming systems which are all RAS based throughout the world. Previous failures of RAS have resulted in considerable learning and understanding of previous failures that are now addressed and to be honest the day of the BEBTA is rapidly fading. Solid engineering coupled with an appreciation for the appropriate design of the business are also contributing factors to major successes in RAS.

The Aquaculture Production Unit epitomises this design philosophy. We have built it to be a semi intensive system constrained by dissolved oxygen levels at altitude to be a self contained RAS fish production system. Individual farmers are already using the APU “tool” in their own unique way – the system is inherently simple enough to allow tweaks and changes to be made to it to suit any situation.