If you thinking of setting up your own backyard aquaponics system, I would strongly recommend the media-filled bed flood and drain aquaponics design (also known as the ebb and flow system).
The flood and drain aquaponics system has been tested and found to be among the simplest and most reliable design for a beginner.
Why The Media-Filled Bed Flood and Drain Aquaponics Design?
All the ammonia rich waste will be converted by the bacteria to soluble nitrates and the remaining solid wastes decomposed into mineral nutrients for the plants’ absorption.
Hence no expensive filtration is required to keep the water clean and free of toxic for the fish.
The periodic flooding provides good and even distribution of the incoming nutrient-rich water throughout the grow bed, delivering the nutrients to the plant roots and bacteria.
The draining of the aquaponics system increases aeration to the media, hence increasing oxygen supply to the plant roots and bacteria living in the media-filled bed.
The water returning to the fish tank also helps aerate the tank water by creating turbulence in the water when it strikes the water surface.
Basic Ebb and Flow System
A basic flood and drain aquaponics system (ebb and flow system) consists of a media filled grow bed that is placed at a height above the fish tank so that water is able to return to the fish tank via gravity.
A submersible pump is installed in the fish tank to pump water up to the grow bed. Such a design is energy saving as it requires the use of only 1 pump.
It is a relatively simple design. However, the drawback is that water may fluctuate a little.
How To Achieve The Flood and Drain Effect?
You can either have a standpipe in the grow bed and timer on the pump, or use an auto siphon in the grow bed alongside a continuous pump in the fish tank.
The 2 standard plumbing systems to achieve the flood and drain effect are:
- Timer-based system
- Bell siphon system (also often referred to as auto siphons as it starts and stop the draining of the grow bed automatically)
The timer-based ebb and flow system is probably the easiest to setup. Essentially, a timer is attached to the pump so that the pump is powered on for 15 minutes every 30-45 minutes. During which, water is pumped into the base of the grow bed via the ‘water-in pipe’ until the water level in the grow bed reaches the level of the ‘overflow drain’, set at 1 inch below the top surface of the grow bed media.
After 15 minutes of flooding, the pump is switched off. Water then drains back through the ‘water in pipe’ at the base of the grow bed and out of the pump back to the fish tank. The drawback of this method is that the intermittent pumping might shorten the lifespan of the pump.
In the bell siphon aquaponics system, the pump is constantly pumping water from the fish tank into the grow bed.
As the water level in the grow bed rises, it fills the interior of the siphon which is located within the grow bed. When the water level reaches a specific height, it overflows into the standpipe within the siphon, and flows out of the grow bed into the fish tank.
In the process, air is sucked out of the bell siphon. A low pressure area is hence created within the siphon, triggering the rapid drawing off of water from the grow bed down to the fish tank.
When the grow bed is almost completely drained, air enters the siphon and the draining action stops.
The grow bed then begins to fill up slowly, repeating the cycle. In order to create the flood and drain effect, the water has to be pumped into the grow bed at a slower rate than it is being drained off.
The advantage of using the bell siphon is that there are no mechanical moving parts or electricity involved, just some simple fittings. The design of the bell siphon is critical to the successful functioning of the siphon and its timely draining effect.
However, the mechanics, design and troubleshooting of bell siphon is often confusing and mysterious to newcomers, and may even still be frustrating to those with experience.
So, do consider checking out my recommended sites to take a look at the design guidelines and step-by-step videos to construct your own bell siphon.
Tip: You should ensure that your grow beds are cycled at least 4 times per hour, or approximately cycling the entire contents of your fish tank in an hour.
Factors influencing the cycle time include the design/sizing of the siphon (if you are not using timer-based system) and the sizing of your pumps (rate of water flowing from your fish tank into the grow bed). The pump of a timer-based system will have to be more powerful than the one in a bell siphon aquaponics system as the same volume of water has to be pumped in just 15 minutes.
It is important to keep the top later of the grow bed media dry to avoid the bottom leaves of the plants from becoming moldy and to avoid an algae bloom on the wet media surface.
Hence the length of the standpipe in the grow bed should end at least 1 inch below the surface of the grow bed media.
To build in addition safety features to prevent any overflow in the grow bed, you can set an additional overflow drain at 1 inch below the top surface of the grow media.
A media guard, which is essentially a large diameter pipe of around 100 diameter with small holes drilled on its sides), should be added over the bell siphon and standpipe in the grow bed.
The purposes of the media guard is to allow for water flow while preventing media from getting into the plumbing system, preventing plant roots from getting in the plumbing and also allowing you to perform maintainenace to the outflow pipings if needed.
However, you need to take a few cautions. The media guard should extend above the grow bed media and air should be allowed to flow freely through to avoid the formation of another siphon.
Hopefully you have found the tips and information on timer-based and bell siphon flood and drain aquaponics configurations useful.
However, in order for this ebb and flow system to function correctly and smoothly, you will need to get the details of various aspects such as siphon design, pump sizing, pipings and fittings right. This may sound like a daunting task for many.
Find Out More…
What I suggest you do now is to check out John Fay’s Aquaponics 4 You for detailed aquaponics design guidelines and step-by-step videos to guide you through the construction of your own DIY aquaponics systems and even your own bell siphon.