Over the course of the last century, our food production system has undergone significant changes. Small, skilled growers have been replaced by multimillion-dollar industries that specialize in only a few crops. Although these large-scale industries can provide affordable food to consumers, the environment suffers due to the reduced variety. Aquaponics, besides utilizing waste, presents a potential remedy for the diminishing diversity.
Let’s begin our journey together by addressing the question: What is aquaponics? Essentially, aquaponics combines aquaculture (fish farming) and hydroponics (soilless plant growth in water) into a single integrated system. In this system, the fish waste serves as nourishment for the plants, while the plants naturally purify the water for the fish. Additionally, the crucial elements of the conversion process are the beneficial bacteria and composting red worms. These act as the “Conversion Team”, found on any moist surface within the aquaponic system. The beneficial bacteria convert the ammonia from the fish waste, which is harmful to the fish and useless to the plants, into nitrites and then nitrates. Nitrates, being relatively harmless to the fish, become excellent nutrients for the plants. Simultaneously, the worms transform solid waste and decomposing plant matter within the aquaponic system into vermicompost.
Here is the remainder of the narrative, arranged step by step:
- Aquaponic Gardening enables home fish farming. You can now feel good about eating fish again.
- Aquaponic Gardening uses 90% less water than soil-based gardening.
- Aquaponic Gardening is four to six times more productive on a square-foot basis than soil-based gardening. This is because with aquaponic gardening, you can pack plants about twice as densely as you can in soil and the plants grow two to three times as fast as they do in soil.
- Aquaponic Gardening is free from weeds, watering, and fertilizing concerns, and because it is done at waist height there is no back strain.
- Aquaponic Gardening is necessarily organic. The natural fish waste provides all the food the plants need. Pesticides would be harmful to the fish so they are never used. Hormones, antibiotics, and other fish additives would be harmful to the plants so they also are never used. And the result is every bit as flavorful as soil-based organic produce, with the added benefit of fresh fish for a safe, healthy source of protein.
Types of systems
Aquaponic systems can utilize various hydroponic techniques, but aquaponics does not include waste-running systems as they do not complete the cycle by reusing filtered water in the fish tank. The prevalent aquaponic methods are Deep Water Culture or raft-based and Flood and Drain or media-based. Although NFT and aeroponic techniques have been used, they are not as common and have limited success because the fish waste solids, regardless of their filtration, will eventually block the smaller tubing in these systems.
The main focus of university research on aquaponics has been on Deep Water Culture (DWC). Dr. James Rackocy at the University of the Virgin Islands has dedicated the past 30 years to perfecting this growing method. In DWC, the fish are kept in separate tanks from the plants. To prevent the plant roots from getting covered in solid waste and suffocating, solid fish waste is eliminated from the water through a settling tank and clarifying filters before reaching the plant raceways. The fish water then flows through a covered raceway with floating rafts. These rafts have holes for net pots with plant roots that hang directly into the water. Freshly planted rafts are placed at the beginning of the raceway. As new rafts are added, they push the older ones to the end of the raceway where they are removed from the water and harvested. DWC is a suitable aquaponic technique for commercial growers because it is relatively simple to plant, maintain, and harvest a large quantity of fast-growing plants like lettuces and some herbs. Additionally, DWC ensures stable water temperatures and pH levels due to the large amount of water required. However, a drawback of DWC is that during the solid filtering process, many essential micro-organisms needed for healthy growth of larger, fruiting plants are lost. Furthermore, while it is feasible to grow larger plants in DWC, it is challenging to provide sufficient oxygen to the extensive root zone of plants that spend their entire lifespan in the water.
The majority of aquaponic home gardeners prefer to use media-based, flood and drain systems. A media-based grow bed typically contains either ½ – ¾” gravel (without limestone or granite!) or expanded clay (Hydroton) and should ideally be about 12” deep. The reason for having these deep beds is to create a multi-layered environment that can support ample beneficial bacteria and composting red worms, which are necessary for maintaining a stable bio-filter for your fish. Additionally, it offers great flexibility in terms of the types of plants you can grow since you never have to worry about the size of your root mass. Some gardeners have even had success growing subterranean plants like potatoes and carrots.
Most media-based grow systems use a timer, bell siphon, or constant flow to control the movement of water through the media beds. In smaller systems, like aquarium-sized ones, the timer cycle is typically 15 minutes of water pumping followed by 30-45 minutes of no pumping. This cycle then repeats. During the pumping phase, water from the fish tank is pumped into the grow bed. The water fills the grow bed up to the top of the standpipe, just below the surface of the media. Any excess water immediately goes back to the fish tank through the standpipe mechanism. This returning water creates turbulence when it hits the water surface in the fish tank, which helps to aerate the fish tank water. When the timer turns off, the pump stops and the remaining water in the grow bed returns to the fish tank through the pump. This period of inactivity allows the roots to dry out and get air, which they greatly benefit from. Then, when the timer triggers the pump again, the cycle starts over.
Fish Tank
When it comes to designing your aquaponics system, the size of your fish tank is crucial as it determines the overall size and flexibility of the system. If you are planning on creating a small, desktop system using an aquarium, you will have limited options for fish that can comfortably thrive in the size of your aquarium. However, if your goal is to cultivate larger, edible fish, it is essential to select a tank that is constructed from strong, food-grade, or food-safe materials. Additionally, ensure that the tank has a minimum depth of 18″ (457mm) and can hold at least 50 gallons (189 Liters) of water. To accommodate ‘plate-sized’ fish (12″ and 1 lb, 300mm and 680g), tanks should have a capacity of approximately 50 gallons (189 Liters) or more.
Any structure that is the correct size and has an EPDM pond liner can be used to create aquaponics fish tanks.
You can utilize a variety of containers for recycling purposes, including but not limited to recycled bathtubs, stock tanks, IBC tanks, and recycled barrels.
To ensure ease of movement, it is important to carefully choose a suitable location for your fish tank. Ideally, the tank should be placed indoors or outdoors in a shaded area. Sunlight is not necessary for the well-being of the fish, and excessive heat and algae growth resulting from sunlight could pose difficulties. Additionally, make sure that the tank is placed on a sturdy surface capable of carrying its weight when filled with water. Considering that each gallon weighs 8.3 pounds (or 1 kg per liter), the tank can easily exceed the load-bearing capacity of the surface you intend to use.
Grow bed
The maximum size of your grow bed is determined by the volume of your fish tank. This is because the plants rely on the fish waste to thrive. If you have a larger grow bed with more plants, you will need more fish waste. Essentially, you need enough fish to support your plants. The recommended ratio between the grow bed and fish tank is approximately 1:1, meaning the volume of the fish tank should be roughly equal to the volume of the grow bed. This ratio can also be expressed as gallons per cubic foot, with the goal of having 6 gallons (22 liters) of fish tank for every cubic foot of grow bed. For example, a 50-gallon (189 liters) tank would be able to support 6 to 8 cubic feet of grow bed. You can extend this rule of thumb up to 2:1 (twice the fish tank volume to grow bed volume), but make sure to reduce the stocking density of your fish tank in order to compensate, as this approach decreases the filtering capability of the grow bed plants in cleaning the fish tank water.
It is not recommended to use metal containers, including galvanized metal, for the grow bed or fish tank. This is because metals can corrode rapidly and disrupt the balance of your system by reducing the pH of your tank. Furthermore, metal containers have the potential to release harmful chemicals into your system, with copper and zinc being particularly hazardous to fish.
What are the benefits?
Aquaponic systems require only one ‘input’, which is fish feed – there is no need for any other fertilizers or chemicals for the plants to thrive. In addition, there are no ‘outputs’ apart from edible food. Since the system is self-contained, no chemicals runoff onto adjacent land, resulting in no harmful effects on waterways or wildlife.
Aquaponic systems can be created anywhere, such as warehouses, underground, or on rooftops, because they do not rely on soil for farming.
The crops are delicious because of the incredible quality of the food, which is a result of nutrient-rich inputs and careful attention. Additionally, the system not only grows a variety of healthy salads but also yields a small amount of edible fish, provided that the fish stocks are replenished with younger fish.
Are there any negatives?
An unfavorable aspect is that not all crops are currently able to be cultivated using this method. Currently, the most successful crops to be grown in these systems are those that grow rapidly and have leaves.
In the meantime, there are individuals who contend that the system lacks a natural element since the plants do not grow in soil. However, it is worth noting that a majority of tomatoes, cucumbers, and peppers cultivated in Europe are actually not grown in soil, but rather in artificial substrates and nourished with water enriched with nutrients.
It is important to acknowledge that although soil is nature’s most flexible medium for cultivation, its health is currently at risk due to climate change and the impact of large-scale farming practices in recent years.
