Picture a scenario whereby you can carry out mixed farming of fish and desirable crops, under the same unit setting. All you have to do is feed the fish, and their excrete alongside fish food leftovers become plant nutrients. Courtesy of aquaponic systems, this pictorial is a reality, whose application helps improve food production in a sustainable and eco-friendly manner.
Below are the requirements for building a deep water culture aquaponic system:
- Choose appropriate fish species for aquaponic set-up.
- Create a water-flow system for the fish species in the tank.
- Install a filtration system to prevent toxic clogging.
- Create growth canals.
- Suspend plants in polystyrene sheets.
- Use a degassing tank if fish stocking density is high.
Read on to learn more about aquaponics design and how to effectively build a deep water culture aquaponics system for hobbyists and even commercial-scale farming practice.
What Are Aquaponics Systems?
Aquaponics systems rear fish and plants together in a controlled environment so both can mutually benefit from each other’s contribution to essential nutrition and sustenance. Aquaponics’ design facilitates a self-sustaining farming practice that mirrors the natural ecosystem.
Essentially, the fish are fed with suitable food pellets, and the waste products they produce are a nutrition source for the plants. The bacteria benefit from the plants by obtaining enough dissolved oxygen, enabling them to carry out the nitrification process of fish excretes.
However, these nutrients are only accessible after the breakdown of fish food leftovers and excreted by natural microbes and bacteria. Because aquaponics involves integrating aquaculture and plant growth in a controlled environment, the farming yields are significantly higher than traditional methods.
In a way, aquaponics eliminates the need for adding chemical fertilizers, as most of the nutrients required for the plants to grow are generated from fish waste and excretions. It would be safe to say that aquaponics is a sustainable technique of farming and one that helps preserve the environment in a purely organic way.
Aquaponics merges aquaculture (fish rearing practice) with crop farming in a water-medium instead of soil, with the aim of co-existence and symbiosis, for nutrients and optimized growth, respectively.
Despite the apparent benefits, installing an aquaponics system can have a high initial set-up cost. However, the grand scheme of things eliminates the need for chemical fertilizers and boosters, which would be rather costly. In addition, the practice is highly scalable, enabling the farmer to benefit from both economies of scale and income from periodic fish sales and crop harvest revenues.
Let’s look at how a basic aquaponic unit works as we indulge in the key components that form an aquaponic system.
How an Aquaponics System Works
An aquaponic system comprises various parts, each with an allocated function that helps the whole system to work as one.
First, the design is such that water containing high fish waste and excretes (effluent water) flows from the fish tank through installed filters and then back to the original fish tank.
So, the effluent water flows through filters where the first solid and leftover waste from the fish tank is removed mechanically. What remains enters into the bio-filters for separation from dissolved wastes.
The biofilters form active sites for natural bacteria and microbes to break down waste constituents that are harmful to the fish to by-products that are nutritional to the plant life. In this case, ammonia wastes toxic to fish are acted upon by bacteria and converted to nitrates beneficial to plants.
The nitrate-rich water is then circulated to the plant troughs and beds before it finds its way back to the fish tank, only pure and good for the fish population.
In a nutshell, effluents from aquaculture serve as a sustainable nutrition source for plants, removing the toxic components of the fish water, facilitating cleansing. Finally, balanced water then flows back to the fish tank.
Types of Aquaponic Systems
Several techniques apply the fundamentals of aquaponics to meet varying user needs and preferences such as farm scalability, budget, and crop type by size.
The main methods in aquaponics include the deep water culture, media-embedded, nutrient film technique, and vertical aquaponics:
Media Embedded Aquaponics
The media embedded method involves using a porous medium, such as gravel or shale substrate, which contains essential minerals and nutrients, set up in containers. The plants are grown in these containers, where water poured in drains all the nutrients in the said medium and is absorbed by the plant roots.
In this case, the medium offers mechanical support to the plant and acts as biofilters trapping and forming sites for waste products. Water containing toxic fish waste flows into the containers by gravity, sipping through the porous medium.
Here, the medium physically filters out wastes and allows plant growth, while the water constituent activates the natural nitrifying microbes. When the water sips out the other end, it is relatively more balanced and rid of harmful wastes.
This water is pumped back to the originating fish tank, resulting in overflow, and more water spills into the media bed. This aspect maintains the continuity of the process.
Media bed aquaponics is suitable for smaller-scale gardening or fruit farming and for plants that develop to have large roots because container sizes can vary.
Nutrient Film Technique
In the nutrient film technique method, aquaculture waste products flow through pipes containing plants with roots dangling in the flowing water by gravity.
This method is most suitable for commercial-scale planting of green leafy crops.
The ability to stack up crop beds on vertical planes contributes to better space efficiency than media beds.
The vertical aquaponic design is best suited for less bulky rooted plants, such as lettuce and strawberries.
How to Build a DWC Aquaponics System
The entire concept of aquaponics systems involves the integration of farming practices to maximize yield and minimal impact on the environment. The aquaponics system is built for sustainability and nearly mirrors how the natural ecosystem operates but in an optimized setting.
Here are the requirements for building a DWC aquaponic system:
1. Choose Appropriate Fish Species for Aquaponic Set-up
Not all fish are suitable for aquaponic farming. Certain fish species, including brackish species, can only survive in saline conditions, which can’t work for aquaponics. Saline environments that support such species are considered hypertonic and unconducive for the growth of most vegetables.
To run an efficient aquaponic system, both the crop and fish harvest need to be profit centers to generate revenue to offset expenses. In some instances, specific fish species have very little market value. Interestingly, regardless of high market value, marine species remain unsuitable for aquaponics.
In addition, the sale of certain fish species in some regions is illegal, such as sunfish, despite aquaponic suitability. The most suitable choice of fish species for aquaponics include tilapia and hybrid striped bass fish.
2. Create a Water-Flow System for Fish Species in Tank
Waterflow is a critical part of the DWC aquaponics system. Water flows from the fish tank by gravity, then through the filtration system, mechanical and biofilters, and pump.
In this case, some of the water is pumped back to the fish tank, while the rest is pumped to the manifold and drained to plants in the canals.
Upon exiting the canals, the water flows back to biofilters with sump and back to the fish tank, more oxygenated and without harmful wastes. The aquaponic water flow system should be designed to have one to four hours of retention.
3. Install a Filtration System to Prevent Toxic Clogging
Any large-scale DWC aquaponic system requires both mechanical filters and biofilters. Mechanical filters remove large wastes, separating them from dissolved fish wastes.
The filtration component of the DWC kit is essential for the removal of both fish food leftover wastes and fish excretions (fish effluent) flowing from the fish tank to the plants. There are two types of filters, which are mechanical filters and biofilters.
Then follows the biofilter, which should be well-oxygenated as they contain nitrifying bacteria that break down toxic dissolved ammonia into nitrates, helpful plant nutrients.
With an appropriate stock density system for the dish in place, filters become unnecessary.
4. Create Growth Canals
Growth canals or troughs, with a recommended depth of between 10 and 12 inches (25.4-30.48 cm) deep for water flow to the plants in the production site, are installed. This allows the plant roots to be carefully submerged into the water supply from the flow system.
The size or length of the canal can vary, but, essentially, a normal-sized polystyrene pipe will get the job done. Narrow longer canals are recommended, as the water flows faster, ensuring nutrients reach all rots across the canal.
The average retention time for water in the canal should be between one and four hours to maximize nutrient uptake by the plants.
In addition, it’s essential to ensure proper aeration of the canals. To achieve better oxygenation, venturi siphons can be installed at the water inlet point to the canals. Kratky’s method that creates an allowance space of 1.18 to 1.57 inches (3-4 cm) between raft and water when implemented allows for sufficient aeration for cooling and oxygenation.
During planting, seedlings are first set in net cups before insertion into the deep water culture kit. However, an exception is made for the vegetable seedling to avoid the risk of transplanting shock.
The entire plant, including roots, are all removed from the canal site in the harvest season. The farmer has to be mindful to clean the raft after harvest for removal of dead plant waste, but also keep it moist.
This precaution helps avoid disrupting beneficial bacterial colonies attached to the undersurface of the raft that would otherwise be destroyed through drying. Also, as a viable alternative, clean and return the rafts in place on the canals after harvesting.
5. Suspend Plants in Polystyrene Sheets
Deep water culture is a method of aquaponics farming that involves the suspension of the crop in polystyrene sheets while suspending its roots in water. In this method, water containing toxic fish wastes flows from the fish tank and goes through the mechanical filter and bio-filters.
After undergoing filtration, water diversion to the manifold follows. This allows for the distribution of nitrates-rich water to the canals, after which they are pumped back through the filters and later to the fish tank.
Due to the high volume of water, it’s easier to mitigate against sudden temperature fluctuations. As a result, both temperature and the pH level remain relatively stable in the deep water culture kit, ensuring the maintenance of an optimal ecosystem for better yields.
With a low stocking density, the deep water culture design doesn’t need the addition of filters.
Most notable about deep water culture aquaponics is the presence of a raft that supports the plant in the polystyrene sheets (rafts), creating a gap between the plant stem and water.
This illustration of the Kratky method leads to better aeration of roots, lowers the risk of exposure to plant infections, and offers cooling during hot seasons. As a result of the floating raft, this aquaponic method is also known as the rafting system or floating system.
During the installation of this technique, some people opt to combine the sump with the filters, which works but is not ideal. Instead, configuring the aquaponic system to have only one main inlet and outlet tank to the biofilters and the canals is the best decision. This setting allows crop roots to uptake more nutrients because of increased water flow.
Deep water culture aquaponics is highly scalable and suitable for the mass production of leafy green crops such as lettuce and basil.
6. Use a Degassing Tank if Fish Stocking Density Is High
A degassing unit comprises a component that releases toxic accumulating gaseous by-products that could be catastrophic to aquaculture and plant-life.
This is a particularly precarious step, depending on the fish stocking density.
Where the stocking density of the fish is high, the incorporation of degassing tanks to the deep water culture system is common practice. This inclusion helps release any gaseous waste by-products like methane.
Advantages of Aquaponic System
There are numerous advantages of creating an aquaponic system, including:
- Sustainable food production
- No soil is necessary
- Doesn’t require chemical fertilizers
- Flexibility in setting up
- Little wastage
- Better chance of production control
Let’s take a look at each of these aspects in more detail:
Sustainable Food Production
As seen in the sections above, aquaponics integrates aquacultures with crop farming in a continuous symbiotic cycle. This aspect helps make the system self-sustaining, with minimal additional requirements.
As a result of the controlled environment and the achievement of a crucial balance in nutrients and ecosystem, both fish and crop yields increase significantly.
You can harvest both fish and crops, all in one go, using this method.
No Soil Is Necessary
Aquaponics, as suggested by the first initial term ‘aqua’ is water-based farming. This aspect means that the technique involves planting crops in a water-based controlled environment without any soil inclusions.
This aspect makes it a good farming alternative for areas and regions without fertile or arable soils necessary for crop growth.
Doesn’t Require Chemical Fertilizers
The nutrients for the crops are all obtained from the breakdown of toxic fish effluents that undergo nitrification by bacteria. This aspect implies that as long as the aquaculture wastes keep flowing, bio-filters containing natural bacteria colonies will maintain nutrient supply to the plants.
In other words, there is no need for additional chemical boosters or fertilizers. This makes the farming practice heavily organic and with no chemical inclusion.
Flexibility in Setting Up
Installation of aquaponic units can be done anywhere, regardless of available space. This implies that the setting can be done outdoors and in enclosed spaces (greenhouse and any space) provided water and light availability.
There is little to no waste when it comes to aquaponics farming. Because most of the resources are recycled back, there is little chance of pollution via harmful overflows and waste runs.
The system works efficiently while effectively utilizing all essential nutritional resources to support fish and crop growth.
Better Chance of Production Control
Aquaponics farming relies heavily upon a controlled setting, where fish effluent is run through filters, and plants absorb nutrients, which enriches the water with dissolved oxygen. The water flows back to the fish tank, balanced with less toxic waste.
This environment is subtly controlled, helping increase the odds of loss avoidance through low yields.
In addition, the controlled environment makes it easier to deal with weeds and other contaminants effectively. Unlike traditional farming or gardening practices that are easily exposed, aquaponics can help minimize biosecurity risks and ensure robust harvests.
Aquaponics methods are designed to suit various needs. For instance, the techniques are tailored to meet all spaces, costs, budgets, starters and professionals, and technological requirements.
Beginners could easily take up a media bed, which is reasonably inexpensive and suitable for subsistence use. Nutrient film techniques (NFT) and deep water culture (DWC) are most suitable for large-scale commercial production operations.
Disadvantages of Aquaponic Systems
Despite the many benefits, aquaponic systems also come with some underlying drawbacks, including:
- High initial start-up cost
- High energy demands
- They require a general understanding of fish ecosystems
- Limited only to certain types of crops
- Risk of system handling mistakes
Let’s investigate these disadvantages a bit further:
High Initial Start-up Cost
For techniques such as deep water culture and nutrient film techniques, the upfront cost of professional installation is high compared to traditional means, like soil farming.
These costs are associated with purchasing core infrastructure such as fish tanks, pipes, sumps, filters, to mention a few primary requirements.
High Energy Demands
In aquaponics, water temperature fluctuations can affect the functions of the entire system. For large aquaponic farms, gravity alone is insufficient for water flow, and energy-driven pumps are necessary.
During low-temperature conditions, detrimental to production, there is a need to maintain optimal temperature for bacterial activity.
These additions increase the electricity use on the farm and the energy consumption cost required to maintain a functional aquaponic system.
They Require a General Understanding of Fish EcoSystems
Aquaponic systems require at least some expertise for the day-to-day running and maintenance of the facility. The know-how to troubleshoot failures, identify inefficiencies, balance the ecosystem, and efficiently run the facility.
Factors such as feed-ratios for suitable nitrate balance, optimal temperature range, and understanding stocking density are critical to the aquaponic infrastructure performance. This aspect leaves many people out of this revolutionizing farming technique, as it requires training that the average farmer would likely not have.
Limited Only to Certain Types of Crops
Not all crops can be grown using aquaponics farming practice. In most cases, vegetables and small fruits are well suited by the practice. This limitation makes aquaponics farming unsuitable for other in-demand crops.
Risks of System Handling Mistakes
In case of any mistakes or unattended inefficiencies, such as power outages without a power-back up, the impacts can pose an irreversible risk to both crop and fish. For instance, exposure to ultraviolet rays can impede the development of nitrifying bacteria that are highly photosensitive, affecting the entire system.
In addition, temperature fluctuations outside the optimal range of between 62.6 and 93.2 °F (17-34 °C) could affect bacterial growth and lower bacterial activity. When the variation occurs, there is an imbalance in the aquaponic system, which affects the aquaculture ecosystem.
Neglects of duty or mistakes risk poor harvest and an uneconomical and underperforming aquaponic system.
- DWC aquaponics has revolutionized farming practices and helped change the farming landscape.
- The merger between aquaponics and aquaculture makes the production of both plant and fish meat environmentally friendly and sustainable.
- DWC is highly organic, yielding healthy and natural foods. There are no additional chemical fertilizers, pesticides, and hormones.
- The method is long-term cost-effective thanks to revenue benefits arising from crop and fish yields.
- DWC farming ensures sustainable mass production of essential crops and improves yields for both plant-based foods and fish meat.
- DWC farming helps reduce marine pressure applied by overfishing due to previous over-reliance on natural marine fisheries.