In this video we will see why and how to build a flood and drain system for your aquaponics system.
A common beginner mistake is to build an aquaponics without flood and drain system. If in the first
weeks it doesn’t seem to make a difference, building a setup without this crucial part is a big mistake
that will probably cause you massive problems. As you know, an aquaponics system is composed of
3 main living creature sections: the fish, the vegetables and the bacteria. The nitrogen cycle is key in
aquaponics and the 3 living creatures play a key role into the cycle of life:
The fish are eating the fish pellet and releasing some ammonia into the water
The bacteria are responsible for transforming this ammonia (toxic for the fish) into nitrite and later
into nitrate (Plant fertilizer).
The plants are then consuming the nitrate and therefore purifying the water coming back into the
Bacteria biomass is critical
Here we realize that the bacteria activity is key and without them the aquaponics ecosystem can’t
work properly. The beneficial aquaponics bacteria (Nitrosomonas and Nitrobacter) are “aerobic”
which mean that they need oxygen to breathe, grow and do their job. In an “anaerobic” (without
oxygen) environment they will simply die and leave the room to other bacteria responsible for the
fermentation, releasing some very bad odours around the aquaponics growbed. Offering an
oxygenated environment to our bacteria is therefore absolutely necessary to the good health of the
The best way to ensure a good oxygenation of the growbed is to put a flood and drain system in
place. A flood and drain system is a device that will allow the growbed water level to move from low
to high several times per day or per hour. When the water drains out of the growbed, the bacteria
are in direct control to the oxygen of the atmosphere and are able to breath. When the water level is
high, the new water is oxygenated so the bacteria can consume the oxygen from the water.
There are 2 very common ways to create a flood and drain system. The first one is the use of a bell
siphon, I made a special video on this specific topic so I invite you to watch it. The other option is to
put in place a timer on your water pump and to place a stand up pipe in the growbed going directly
into the fish tank. The stand up pipe will contain a little hole at the base allowing a little water flow
to drop into the fish tank allowing the growbed to drain when the pump is off. This hole water flow
is still smaller than the pump water flow, therefore when the pump is on, the water flow coming into
the growbed will be higher than the water flow going back into the fish tank and therefore the water
level will increase to reach the top of the stand up pipe (also called stand pipe).
The main advantage of the timer’s pump technique is the convenience to build. The limitations are
that is turns the pump on and off several time per day which is not very good and generally decrease
the pump lifetime. The other negative point is that it doesn’t generate the same flush as a bell
siphon, it mainly drains the system without generating a real flush effect which helps to avoid the
growbed media to clog with time. The pump on timer system is still a very good option for anyone
who want an efficient and quickly made setup.
This video is a key video to understand how to build your own aquaponics system without the bell
siphon as it’s the best option for the ones who want to create a setup very easily.