During our Vietnamese trip we had the chance to Visit Celine and her team around Hoi an. They have a nice aquaponics system composed of an NFT aquaponics system, I have published a nice video there. They are also working on a Deep Water Culture (DWC) aquaponics system also known as raft tank and are running a DWC hydroponics system.
DWC systems are very well adapted to large scale production such as large scale Aquaponics or commercial aquaponics.
Deep Water Culture (DWC) aquaponics also known as “raft aquaponics”
In this article I would like to develop this specific technique. It consist of growing plants fixed on rafts floating on the surface of a “Deep Water Tank” equipped with aeration. The aeration in those tanks is very important as it brings a constant supply of oxygen to the vegetables roots but also to the bacteria living on those roots. The Deep Water Culture aquaponics systems generally contain a fish tank and a filtration system (mechanical and biological). Indeed we want to keep the DWC tanks very clean. The water movement into the DWC is generally very low. If we don’t use any mechanical filtration between the fish tank and the DWC tank, all the organic particles such as the fish poo will settle down into the DWC tank.
Easy to harvest
The culture into a DWC tank is simple. The plants are simply floating on rafts. You can simply harvest the number of rafts you need at one end of the DWC tank and put new rafts into the water with young seedlings at the other end.
The DWC offers a very large surface area for the bacteria thanks to the plants roots. I still recommend to add a biological filter into those systems as the actual surface area offered by the plants is very difficult to estimate and if for any reason the plants die, you will lose the whole bacteria support.
A peculiar material choice
During this visit, Celine explains us that she is using polycarbonate boards to build the structure of the DWC tank. This is an original material to build a tank. We understand that she probably recycled some unused material. This is not a material that I would recommend as I am not sure how it resist to the water pressure. We generally find that wood is used for structure purpose. A liner is then applied inside the structure to waterproof the tank. The floating raft are polystyrene boards. We developed this topic during the visit of Clive’s multisystem Aquaponics here
Hydroponics vs aquaponics
Celine is already growing a multitude of crop in the hydroponics system including basil and lettuce but she will be able to double the production thanks to the Aquaponics DWC system. It is particularly interesting as they are using 2 Deep Water Culture aquaponics systems (one Hydroponics and one Aquaponics) so they will be able to compare the growth, and quality of the production.
You will probably be interested to discover Jonathan’s six steps to build and manage an Aquaponics system. Click here to access for free! Thanks and good reading 🙂
