Aquaponics System Types: The Differences Between F&D, NFT and DWC

I assume that when you've been researching aquaponics systems, you've come across terms like F&D (Flood & Drain) - the classic flood and ebb system, NFT (Nutrient Film Technique) and DWC (Deep Water Culture), also known as Floating-RAFT? The whole thing confused me at first because I simply didn't know which design I should use for my first system or what these different variants are actually good for. To make it easier for you to get started, I'd like to explain the differences and the possibilities for sophisticated combinations in more detail.

1) Flood & Drain – the classic

The high and low tide principle is the classic among aquaponics types. This is simply because you kill two birds with one stone. Firstly, with the aquaponics grow bed you have plenty of space for planting plants. Secondly, the planting bed filled with grow media is simultaneously the mechanical and biological filter, which returns the cleaned water to the fish tank when it is emptied. The plants are planted in a substrate suitable for hydroponics (grow media) and the roots take hold in it. However, no soil is used in hydroponics, as this would compact too much through regular watering and this would cause rot. Clay granules such as classicplanting clay are usually used.

How does an aquaponics flood and ebb system work?

Grow beds are the basic requirement for an ebb and flow system. The planting bed container is usually higher than the fish or sump tank and is filled with planting clay, clay granules or gravel. The grow bed not only contains planting clay, but also the so-calledBell siphon . A clever part that allows the grow bed to empty the bed without electricity when a desired water level is reached and then fill it up again.

The grow bed is filled through a supply line from the fish tank. A ball valve ensures that the correct amount of water is supplied. The standpipe of the bell siphon defines the desired water level around 5cm below the substrate level. As water gradually flows into the opening of the standpipe and begins to flow out through the siphon bend, the so-called siphon effect is created after a short time. The resulting negative pressure empties the entire grow bed until the openings of the siphon bell suck in air again and the process is interrupted. The grow bed then fills up again.

What exactly happens during this process?

Every time the maximum water level is reached, the roots of the plants in the grow bed come into contact with nutrient-rich water from the fish tank. In this case, the plants benefit not only from the nutrients, but also from the oxygen content of the water. Because the water is evenly distributed in the cavities of the grow media, it comes into contact with the surface of the grow media, which is densely populated with microorganisms. This not only means that solids from the water get stuck between the gravel or clay granules, but a biological process also takes place in the background. The water enriched with ammonium by the fish excrement is converted by the microorganisms into nitrite and then into nitrate. This is a process that turns the contaminated water back into non-toxic, neutral water. An ingenious mechanical and biological filter at the same time!

2) DWC - Deep Water Culture

These cultures are also very popular in aquaponics systems. In this case, containers filled with water serve as a kind of "swimming pond" for the plants. The plants are placed on a floating raft on the water surface in net pots. The nutrient-rich fish water from the aquaponics system circulates through the container. The roots of the plants meander through the approximately 30cm deep water basin and are continuously ventilated from below with an air pump. This is very important in this case. If the roots of the plants do not have enough oxygen, root rot can occur.

3) NFT - Nutrient Film Technique

NFT is one of my favorite variants. The name already tells you that it is a water film. This water film runs through NFT channels. These are rectangular or round channels in which the water often flows from top to bottom purely by gravity. In this case, the plants sit in net pots with clay granules or gravel and are supplied with nutrients through the water.

Of course, it is necessary that the water is first pumped to a certain height. This is done with a pump, of course. Since aquaponics requires at least one pump anyway, NFT in combination with an F&D is particularly suitable. For example, I like to use NFT after the siphon bend of the Bell siphon. If the water has to flow back into the fish tank from top to bottom anyway, I often like to use the height difference to make a small detour in an NFT channel.

What is your preferred form of cultivation? What have you tried and what experiences have you had with it? Please share your experiences with us. You can find the comment box below!