DESIGN AND BUILD
The grow beds
Water flow and positioning of the grow beds Water flow is the most important part of proper system design, and the exact positioning of the grow beds has a major impact on this. Therefore it should be considered carefully and, if possible, an expert should be consulted. The grow beds should be positioned after the biofilter and before the water is recirculated to the fish tank. Consider how the water will flow from the grow bed into the fish tank.
· Aqu@teachThe fish tank
The basic components to consider are fish tanks, the sludge removal unit, the biofilter, the sump, plant beds, pumps, and piping. The function, required materials, and location of each of these, and their interaction with other components, all need to be considered. The interaction among the components, for example, will determine the number of pumps that will be required. The fish tank will be the home of the fish for a relatively long period of time, so it should be chosen with care.
· Aqu@teachThe biofilter
The biofilter is the heart of every recirculating aquaculture system. Fish health, and therefore economic success, depend on correct operation of the biofilter. High ammonia and nitrite levels in fish tanks can be caused by several factors. One of these can be poorly designed or sub-optimal operation of the biofilter (too small, not mixed evenly, nitrate levels too high, pH too low, intoxication of the biofilter by salt or medical treatment, aeration too low or too high, etc.
· Aqu@teachStarting to design an aquaponic system
Do not be confused by the great variety of designs for aquaponic systems which you may encounter in the literature or by browsing the web. When planning and building an aquaponic system, it is necessary to follow the basic principles in order for the system to function properly. There are big differences between systems in terms of investment costs, maintenance and operating costs, reliability, health and safety, potential for fish and crop growth, and total workload.
· Aqu@teachSolids separation
The following decisions need to be made during the design stage: Is a separate solid removal step necessary? In systems with a low fish stocking rate, a media growing bed can remove solids and act as a biofilter. However, over time, clogging and anaerobic areas will occur as the amount of solids increases. What is the appropriate device for solids removal? Waste particles in the water can be of different sizes, which affects the technologies used to remove them.
· Aqu@teachOperating an aquaponic system
Basic system maintenance and operation procedures To ensure that the aquaponic system is running well one should prepare clear operating, maintenance and troubleshooting instructions (manuals), and also checklists of daily, weekly and monthly activities for which records should be kept. This way, different staff members will always know what to do. All observations and tasks performed need to be entered (with specific dates) in a dedicated record book, that must be stored in a visible place.
· Aqu@teachFeasibility study: location and infrastructure considerations
Table 2 outlines the most important location and infrastructure considerations when designing a new aquaponic system. Aspect Description Site stability and foundations Water is heavy. Choose stable and level ground for building your aquaponic system. If the ground is not stable, the foundations will be unstable and leaks could occur because of movement of the pipes. Climatic conditions at the location Consider how to protect the aquaponic system from extreme weather events.
· Aqu@teachConnections, water movement and aeration
Plumbing PVC pipes are most commonly used for plumbing. They are available in many standard sizes, are cost-effective, easy to cut and adapt to a wide range of adapters and connectors, and also usually last a long time. Other materials could also be used, but they must be safe for both the fish and the plants, and for food production. Some general advice about pipes: pipes have to be ‘just right’ – if the pipes are too small there will be a problem with leaks, and if they are too big the solids will not get flushed out because the water pressure will be too low
· Aqu@teach