Aquaponics System Designs
While there are many different ways to configure an aquaponics system, there are some standard design prinicples. For example, most aquaponics system designs separate the fish tanks and plant beds. In addition, the fish tanks and the plant beds are located at different elevations in order to take advantage of gravity in circulating the water. The density of the fish and plant populations also need to be kept in balance so you do not either under nourish the plants or pollute the fish tank water. Starting from these basic principles, there are then many different variables that can be applied to customize an aquaponics system.
The size of fish tank (250 gallons is the minimum recommendation) determines how much produce can be grown and should be matched to the size of the plant bed. At the most basic level, the fish tank is simply a container to hold water that is safe for raising fish. This container can take the form of a standard aquarium, a backyard pond, or really any “tank” made out of fish safe materials. The water return can be through pipes or more decoratively take the form of a waterfall or stream.
Other variables include the use of supplemental filtration, the location and arrangement of the plumbing to move the water, the type of plant bed and the amount and frequency of water circulation and aeration.
In general, an aquaponics system is an offshoot of well established hydroponic designs that have been adapted to accommodate fish and filtration. What follows are descriptions of 2 popular alternatives:
Raft SystemIn a raft aquaponics system, plants are grown on Styrofoam boards (rafts) that float on top of water. In most cases, this is in a tank separate from the fish tank. Water flows continuously from the fish tank, through the raft tank and then back to the fish tank. There is usually some means of mechanical filtration between the 2 tanks to remove bulk debris.
Beneficial bacteria live throughout the aquaponics system, converting fish waste products from ammonia to nitrite and then to nitrate. The nitrates provide nutrients which are consumed by the plants which removes the nitrate filtering the water. The extra water in the plant bed tank also provides a buffer for avoiding potential water quality problems. Most commercial aquaponics systems use some variation of this method, which is well established and highly productive. Hobbysts who are inerested in production also use this design
Media BedIn this type of aquaponics system, the plant bed is a tank or container that is filled with gravel, or some other filter media. The plants’ roots are embedded in the gravel and the water either runs continuously or the bed is periodically flooded from the fish tank. The filtered water then drains back to the fish tank. The continuous method is preferred if you are using a decorative display such as a waterfall to return water to a backyard fish pond. The flood and drain method will save electricity, water loss and operating hours on the pump. The Media Bed design is simple to operate and build. It is used by most hobbyists who operate an aquaponics system in their backyard. Beneficial bacteria reside in the filter material and all waste, including solids, is broken down within the plant bed. Supplemental mechnical filtration can be added but is not required. This type of aquaponics system involves fewer components and is simpler to build and operate but the output of food per square foot is much lower than the raft system.
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