The basic flood & drain aquaponics system is the most common system layout.
There are probably thousands of them in use throughout the world and most of them (to a greater or lesser extent) produce fish and plants.
The system comprises a fish tank, a submersible pond pump and one (or more) flood and drain grow bed(s).
The grow beds are positioned in such a way that they drain directly back into the fish tank and the flood and drain cycle is controlled by a timer or an auto-syphon.
The pump, which is located in the fish tank, lifts water into the grow bed(s). Once the water reaches a pre-determined level, the pump will stop (or the auto-syphon will start) and the grow bed(s) will drain back into the fish tank.
The advantages of the Basic Flood and Drain layout include:
- Its simplicity
- It’s cost effectiveness
The disadvantages of this layout include:
- The need to provide support stands (and/or to partially bury the fish tank) in order to place the grow bed(s) above the top of the fish tank.
- The number of grow beds limited by the available fish tank volume (without resorting to spider valves and other expensive solutions).
- Fluctuating water level in fish tank.
- Raft tanks can be used in conjunction with (or in place of) grow beds.
- Continuous flow watering of the grow bed can be used in place of flood and drain irrigation.
- The advantage of continuous flow watering, or raft tanks, is that you do not experience the fluctuating fish tank water levels that you do with flood and drain grow beds.
- Where you elect to use raft tanks or flood and drain media-based grow beds, it is advisable to attach a trickling bio-filter to the system to underpin nitrification and to enhance aeration. While this is advisable for all aquaponics systems it is particularly applicable to small ones.
- Without mechanical filtration, this layout (as with all aquaponics systems) will be limited in terms of stocking density and nutrient production.
In 2007, we designed the microFish Farm (a variant of the basic flood and drain design) which is the subject of my next post.