Intro To DWC Floating Raft Systems Made Easy

Deep Water Culture Aquaponics (DWC) is a type of aquaponics that refers to the method of growing plants where the roots are constantly submerged deep in water. Also known as the Raft System, or Floating Raft Method, DWC is one of the easiest yet most efficient types of aquaponics. The technique offers several great benefits, as well as couple of disadvantages, so it’s important to fully understand the process before choosing deep water over other aquaponics solutions.

Aquaponics is a growing technique that utilizes aquaculture and hydroponics to create a self-sustaining ecosystem that provides consistent optimal conditions for growing almost any type of plant. Growing using the aquaponics method can be achieved through one of three different techniques. All three types of aquaponics have useful application depending on the scenario. To determine what technique would be best match your requirements, specification, budget and ultimate goals, it’s advisable to spend some time researching each technique in-depth; to the point you fully understand the different approaches, so you can then make the most informed decision.

Aquaponics and DWC/The Raft Method

The three types of aquaponics setups are as follows:

Media Based System (Media Based Grow Bed or Flood and Drain) – Easy to operate, common for smaller scale, in-home DIY setups.
NFT (Nutrient Film Technique) – Adapted from effective, modern hydroponics setups, commonly used for commercial setups as well as urban locations where food production and space can be problematic.
DWC (Deep Water Culture, or Floating Rafts, Raft Aquaponics) – One of the most efficient designs; can be configured in several ways, can fit in compact spaces and/or has the ability to scale up easily.

NOTE: If you’ve attempted to research the types of aquaponics and their application, and have scoured through several resources then it’s likely you’ll have come across conflicting information regarding DWC and its suitability for large-scale setups.

Without singling out any particular source, let’s try put this matter to rest once and for all. The two claims sit firmly at opposite ends of the spectrum:

One states that DWC is a top choice for commercial operations due to its ability to mass-produce.
The other says that DWC setups aren’t suitable for large-scale operation due to difficulties scaling up.

These two claims aren’t just at opposite ends of the spectrum, they directly contradict each other. So let’s break down exactly why these claims have been made to see if we can decipher which actually applies.

A deeper look into this issue quickly uncovers the confusion. DWC itself refers to a group of at least three techniques, two of which, bubble and the Kratky Method have trouble scaling up, whereas the third method RDWC, applies a different approach that does allow the system to be scaled up, and rather easily too.

So, what it really comes down to is your requirements, space limitations, and budget.

Image Credit: New Agrarian, Walkthrough of our Aquaponics System (Tips and Tricks)! 2021.

What is Deep Water Culture Aquaponics aka Floating Raft Method?

Deciding whether DWC is right you comes down to several things; the types of plants you wish to grow, the available space you have, and your available schedule. Although these systems are virtually self-sustaining, they do require regular maintenance, and should anything go wrong immediate attention is crucial for the survival of the plants and fish.

Types of DWC/Floating Raft Systems

There are three different configurations of deep-water culture aquaponics, each suitable for slightly different applications. These include:

Bubbleponics – this system works by adding a water pump inside the reservoir to move the water to the top of the net pots so it can hydrate from the top then trickle back down into the reservoir. This speeds up the beginning stages of the grow cycle when the plants roots are still too short to absorb nutrients efficiently.
Kratky Method – almost set and forget, this setup utilizes an air gap between the water and raft; this serves several functions; it allows the plants to absorb both water and oxygen, the gaps also gives room for the plants to respire.
Recirculating Deep Water Culture (RDWC) – this solves the issues other two systems have with scaling up easily by utilizing a central reservoir and external buckets containing 1-3 plants. Expansion is as easy as adding buckets, water, oxygenating, and calibrating the system.

No matter what DWC system you chose to construct, you’ll find a number of advantages, and just a couple of disadvantages, that could help sway your decision. Of course it’s advised you carefully consider these points and how each affects your particular scenario before committing to the initial costs of setup, which for all systems except the Krakty Method, isn’t necessarily cheap.

Advantages to DWC

Easy to set up: whist the technique might sound complicated and advanced; it’s actually really simple to set up with affordable, off the shelf components
Versatile space requirements: although DWC is often the choice for large-scale operations, these systems can be setup in compact spaces; making them suitable for home aquaponics and other small scale aquaponics aquariums
Efficient nutrient uptake: Net pots allow the roots to grow in all directions; this promotes a healthy root system that’s more efficient at nutrient uptake
Fast growth: since the plants are constantly submerged in the nutrients they require, which in turn makes the root structure as hardy as can be, growth of the plants can be extremely rapid once the system is operating optimally
Fully automated: again, once your system is properly configured, it will self regulate the correct amount of nutrients and oxygen. But it’s important to note that, whilst in theory, the ecosystem should balance itself out, there are many factors that can disrupt the symbiotic relationship that keeps all levels in check, therefore strict monitoring and maintenance are required to ensure the system runs optimally.

Disadvantages to DWC

There aren’t too many disadvantages to setting up a DWC system, however when things go wrong it can have devastating consequences.

Difficulty growing beneficial bacteria: A lot of DWC systems can have trouble growing sufficient amounts of bacteria due to the lack of internal surfaces available for the bacteria to colonize.
Broken pump: Since the plants are submerged in water 24/7, the water must always be oxygenated. This means if the water pump breaks, you’ll have very little time to rectify the situation before all living organisms in the system will suffocate and die.
Risk of disease: Although DWC systems can be self-regulating, it’s not a process completely free of input. DWC setups have a higher risk of developing diseases and therefore can sometimes require solution changes to keep algae growth and the development of disease at bay.

What Species Of Plant Are Best for DWC Aquaponics?

The main goal of running an aquaponics system is to grow and harvest plants, therefore what type of plants you chose to grow in your aquaponics system should be the first consideration.

Despite what the deep-water name may suggest, DWC is best suited to growing short rooted, and edible aquatic, plants such as:

Lettuce and other salad leafs
Cabbage
Herbs such as basil and watercress
Cucumbers
Cauliflower
Strawberries
Tomatoes
Peppers

What Species Of Fish Are Best for DWC Aquaponics?

To ensure you’re selecting the most suitable fish for your DWC aquaponics you’ll want to research safe temperatures and growth rate to ensure their suitability to the environment you’re about to place them in. Common choices for hardy fish that thrive well in an aquaponics system include:

Tilapia
Trout
Catfish
Koi
Goldfish

Some may question whether the fish in your aquaponics system can be eaten, and the answer if of course, yes! The main purpose of aquaponics is efficiency, and since fish are a great source of food, using edible species for your own benefit is all part and parcel of this eco-friendly project. On the other hand, there’s also no issue with placing beautiful looking fish for more aesthetic reasons.

Why Don’t Aquaponics Plants Drown?

So, why don’t the plants drown? Unlike soil potted plants that can be overwatered and will eventually die, DWC plants are constantly submerged in water, which may seem impossible when considering how plants typically react to a little extra hydration.

So, why exactly don’t these same plant species die when grown in an aquaponics setups?

The key lies in the levels of oxygen in the water. Just like fish require oxygenated water to breath and survive, so too do plants. DWC plants are only able to survive in water when it is provided with enough oxygen and nutrients, as well as sufficient lighting and suitable, stable temperatures.

Therefore a deep-water culture aquaponics design must include a source of oxygen; typically achieved by installing a water pump to power a fountain, waterfall or cascading series of steps that allows water to drop and aerate.

When it comes to bubbles, the more the better. Air stones are a simple and easy way of getting more bubbles and therefore more oxygen out of your pump. These porous rocks create extra bubbles as water is passed through it to add an extra burst of oxygen to the system.

DWC The Floating Raft System Conclusion

DWC might seem like a complicated way of growing plants, and when compared with traditional methods, it could be classifed as such. However, with a little research you’ll quickly realize the technique is relatively manageable, and more importantly, as well as being highly efficient, the method offers a few configurations that are suitable for different scenarios.

If you’re considering setting up a DWC aquaponics system, you’ll want to consider what plants you wish to grow, what fish you’d like to rear, and what type of DWC configuration best suits your space and your schedule.

For those who’re interested in building their own DWC aquaponics system, check out our “How to DWC Aquaponics” article for more information on what factors to consider, and how to go about constructing your first deep water ecosystem.

Image Credit: freepic.com

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