Aquaponics is a form of agriculture that combines aquaculture and hydroponic farming in a closed-loop gardening system. Fish waste, in combination with a biological filter that facilitates the nitrogen cycle, provides nutrients necessary for rapid plant growth. In turn, the plants purify the aquatic environment by removing the waste. Depending on the agriculture goals, either the vegetative produce or food fish (or both) can be periodically harvested from the system. In the aquarium hobby, aquaponics may be used to maintain a healthy aquarium ecosystem while producing ornamental fish and food for the hobbyist.
Aquaponics systems can be proven at home using goldfish, cichlids, or large numbers of small tropical fish. It can also be scaled to backyard gardens with koi, or even large-scale agricultural operations using food fish such as tilapia, perch, or rainbow trout.
This article provides an overview of aquaponics and highlights its overlap with the aquarium hobby. It also includes the building process of a small home aquaponics system.
Aquaponic farming practices can provide food security in areas where it is difficult to grow vegetables due to climate conditions or poor soil quality. Indoor, soil-less aquaponics offers a year-round growing season that uses less water and energy than conventional land-based agriculture. Aquaponics can be set up anywhere with access to freshwater and sunlight. Moreover, applying greenhouse technologies and harnessing sustainable energy sources can help scale aquaponics and bring produce to larger markets. In addition, pesticides and herbicides are not used as in traditional farming, resulting in plants healthier for consumption, reducing risks to fish health, and minimizing environmental impacts. Aquaponics can also help prevent the eutrophication of lakes and ponds caused by fertilizer runoff from traditional farming practices, as its closed-loop design keeps fertilizers contained. Overall, aquaponic practices contribute to diversifying food production and increasing food availability.
Food Security-Related Aquaponic Projects in Canada (2016, 2019):
Mississauga, ON: Aquaponics has been shown to produce 10,000 servings of lettuce and fish annually to supplement food bank inventories.
Takhini Hot Springs, YT: Utilizing geothermal energy sources, ornamental fish classify the operation as an aquarium rather than a fish farm to avoid regulations.
Challenges and Diversification (2017):
However, it is argued that aquaponics is not a catch-all solution to all agricultural challenges. Diversifying agricultural practices is often the best approach for food security.
Hay River, NWT: Grazing animal-based food production still provides calorie-rich foods in areas with limited infrastructure. Additionally, startup investments and energy costs can be barriers to aquaponic projects.
Profitable Farming Strategies
The aquaponics industry continues to show promise in specialized areas like microgreens, protein powders, and aquarium retail.
Current aquaponic projects from Greenhouse Canada (2023):
Croxall Farms (Huntsville, ON): They grow a variety of greens, herbs, strawberries, and peppers while raising salmon, tilapia, Arctic char, and prawns for food, as well as koi fish for aquarium retail. They also sell Aquanure fertilizer, derived from concentrated fish waste.
Rafferty Farms/ Earthis Ltd. (Okotoks, AB): This farm focuses on growing basil, mint, and microgreens for grocery stores and restaurants while raising 175 pet koi in a 60,000L pond. They also sell a pesto paste. They utilize geothermal, wind, and solar energy to offset operating costs.
Other ventures work with Rainbow trout and water lentils, also known as common duckweed (Lemna minor), a floating pond plant rich in protein and vitamins, ground into a powdered protein supplement. However, due to differing water temperature requirements, trout and duckweed require separate (decoupled) circulating systems, with mixing to deliver dissolved nutrients to the plants.
SYSTEMS & AERATION
All aquaponic systems share a common principle: nutrient-rich water circulates through growing media or contacts the plant roots before cycling back into the fish reservoir. Aeration is crucial to healthy aquaponics production, as it increases dissolved oxygen, benefiting fish respiration, preventing plant root saturation, and supporting the biological filter. Two system designs, the Deep Water Culture (DWC) and Flood & Drain (Ebb & Flow) are described below.
Deep Water Culture (DWC): In this system, plants are suspended in plastic net pots at the water's surface using floating rafts of insulation foam or grown directly in a deep bed of well-drained growing substrate, such as expanded clay pebbles, constantly flooded with deep water. Plant roots are constantly submerged in nutrient-rich water while also needing access to air. Primarily, air pumps are used to deliver aeration to the roots, while water pumps, float valves, and innovative plumbing standpipes ensure a constant waterline.
DWC: Provides oxygen using an airpump to release bubbles into the water from below the raft-suspended plants (1A/1B).
2. Flood & Drain (Ebb & Flow): In this system, plants are suspended in plastic net pots at the water's surface or grown directly in a bed of well-drained substrate. This method involves periodically flooding the grow table and allowing the water to drain, ensuring proper aeration by exposing the plant roots to the atmospheric air, before flooding again. Specialized standpipe drain plumbing such as the Bell Siphon or Herbie Overflow, with water pumps and timers, are used to move water between a grow bed and a reservoir to achieve this effect. Air pumps are optional with this approach. Other innovative approaches can use aquarium automated top off (ATO) concepts using float switches and float valves to control water movement.
PRESS PLAY TO OBSERVE HOW THE BELL SIPHON & HERBIE STANDPIPE FLOOD & DRAIN
Ebb & Flow Video: Flooding is done without (2A) or with (2B) a timer depending on the plumbing. Both the Bell Siphon and Herbie Overflow methods use a reservoir and a water pump to deliver nutrients. The reservoir is used to house fish.
Other aquaponic system designs can be researched to find what will work best for each application. In addition to water pumps and air pumps, other equipment to consider include lighting, heating, feeding and water quality monitoring, similar to keeping a planted aquarium.
Aquaponics AT HOME
I built an aquaponics system using a 2' x 2' (60cm x 60cm) flood table with a bell siphon overflow, using a customized aquarium as a reservoir and stand. The system produced leafy green vegetables and herbs while raising tetras, gouramis, and catfish in a planted aquarium.
1. GROWBED
2’ x 2’ Hydroponic flood table
Corrugated plastic with 4" holes to suspend net pots
Net pots filled with Hydroton media that doubles as a wet/dry biological filter
2. PLUMBING
Bell Siphon Overflow: ebb & flow plumbing drains and fills the growbed to provide aeration to plant roots and deliver water
Bulkheads ¾” & 1” drain and irrigation tubing
Continuous pump operation
3. RESERVOIR
20g Aquarium - reservoir should be at least 2X the growbed volume, in this case it was 5-6X the volume)
4. BIOLOGICAL FILTRATION
Hamburg Matten Filter (HMF)
5cm thick foam bent into the aquarium corner, secured with 2 pieces of 90-degree plastic trim and silicone.
Refer to Swiss-Tropicals; Ebay for foam; hardware store for trim.
Quiet One 1200 water pump (317 GPH), provided adequate head-height.
50w Heater (for tropical fish)
Want to learn more about the HMF filter? Read another article on HMF filters available here:
5. LIGHTING
Indirect light from a window.
AI Sol LED (cool white light) was repurposed.
2 x 24W t5HO Sunblaster 6500K (supplemental light in the winter).
25 watts per square foot.
Adjustable light stand made with electrical conduit PVC.
6. FISH
I chose to keep a population of popular community fish including tetras, gouramis, and catfish. The fish you choose for the system should match the same temperature and pH tolerances as the hydroponic plants. If heavily stocked, the fish should be tolerant of high nitrate and low dissolved oxygen (DO).
Temperatures 20°C < 30°C
pH 6.5-7.5
Tolerant of high nitrate and low dissolved oxygen.
For the community aquarium, also consider species school size and behavioural compatibility when stocking.
Suggestions of common fish in the aquarium hobby: | Common fish in larger-scale aquaponic systems: |
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FEED YOUR FISH!
Plant growth is proportional to the stocking density & quantity of food.
Feed 1-5% of fish mass per day.
Use an automatic feeder.
7. PLANTS
Depending on the nutrients and minerals present in your source water, some plants may thrive better than others. Be prepared to experiment with different plants to assess their tolerance to your water conditions, or research complementary species to minimize competition between plants.
Plants can be sprouted in a high-humidity environment before being transferred to the net pot growing media, or they can be started directly from seed in the net pots. A coconut fibre starter plug or mineral wool can be used to support the seeds during germination.
I was successful with the plants indicated in bold below. There are many plants that tolerate hydroponic growing conditions. Depending on the combination of plants, nutrients may be used at different rates making it important to observe your plants for deficiencies.
PLANT OPTIONS:
Spearmint
Sweet Basil
Parsley
Swiss Chard
Chives
Kale
Green Onion
Lettuce
Tomato Vine
Chilli Peppers
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Certain fish, such as tilapia, catfish, and koi, are commonly paired with leafy greens and tomatoes. Cool-water fish, like trout and perch, pair well with herbs and spinach. However, you are encouraged to grow a variety of vegetables to see what works best with your community aquarium!
GROWING RESULTS
8. FERTILIZATION & DEFICIENCIES
If the nutrient demand of the plants exceeds the capacity provided by the fish stock, supplemental fertilization may be required to supply additional nitrogen and trace minerals, such as iron.
Most macro-fertilization, like nitrate and phosphate, is provided by fish waste through biological filtration. However, a low fish stocking density may not generate enough nitrate to sustain rapid plant growth. Trace minerals are also more likely to be depleted with fast-growing plants, so a micronutrient fertilizer designed for aquarium plants is a good starting point if growth slows down, or plant leaves are abnormal in shape or colour (see Table 1). Larger systems can benefit economically by mixing dry fertilizers (see Table 2) with reverse osmosis water for nutrient supplementation. If over-supplementation occurs, a water change can dilute the excess. Water removed from the aquaponics system can also be repurposed to water houseplants or a vegetable garden.
Table 1. Critical nutrients (nitrate, iron, calcium, potassium, phosphorus, magnesium, boron, zinc, manganese, and copper), their significance to plant growth, signs of deficiencies, and replacement supplements.
The biological filter supports the nitrogen cycle, which helps maintain a safe environment for your fish. However, over time, it can also lead to the acidification of the water. Depending on your water source, regular water changes can help stabilize and buffer the pH to remain between 6.5 and 7.5. Natural, aquarium-safe products such as crushed coral can help raise the water's pH, while driftwood or dried botanicals can be used to lower it.
Low fish load or a heavy plant demand can result in macro & micro nutrient deficiencies requiring supplementation with fertilizer.
Aquarium fertilizer tablets and liquid fertilizer dosing are easy and safe methods used to supplement nutrients in small aquaponic systems.
Ideal pH = 6.5-7.5 ensures nutrients remain available to the plants (highlighted in yellow).
The "Dirted aquarium" concept uses a layer of organic soil under the aquarium substrate, which could provide a long-term nutrient release from the fish reservoir.
Table 2. Critical nutrients (nitrate, iron, calcium, potassium, phosphorus, magnesium, boron, zinc, manganese, and copper), their ideal level (concentration), replacement supplements, and directions to dosing the supplements.
Note: Supplement doses are listed in grams based on increasing the nutrient concentration in 1000L (approximately 250 gallons). To reduce the dosing amounts to 100L (approximately 25 gallons), use the same number of grams, but multiply the effective ppm result by 10. For example, in 100 litres, 1.32 grams of calcium nitrate, will increase nitrate levels by 10 ppm.
9. MAINTENANCE & MANAGEMENT
By monitoring water quality for ammonia, nitrite, nitrate, and pH, you can ensure the plants and fish are provided the basic requirements to thrive. Standard aquarium maintenance methods can be used to address water toxicity while taking care not to disturb or sterilize the biological filter. If these water quality variables are maintained within ideal ranges and the plants still show deficiencies, you can quickly identify what nutrients to supplement. Similarly, if fish health declines, it is important to act quickly by isolating the affected fish for treatment.
System components can fail. To prevent unexpected pump failures, clean them a couple of times per year and inspect the plumbing periodically. Other components like lighting, heaters, and power strips should be checked regularly to maintain consistent performance. Redundancies or backup pumps, lighting, and heating options should be available in case of an emergency.
Some challenges and limitations include the initial build costs, ongoing operational costs, and the technical balance between aquaculture and hydroponic components. Building a system involves the cost of equipment, seeds, growbeds, lighting, and more. It is recommended to plan the system build beforehand and gather components over a couple of months before starting. The operational costs of a home aquaponics system will be similar to 2 aquariums of comparable size. Larger-scale operations depend on greenhouse technologies and other renewable energy sources, which can also be expensive initially. The technical balance requires some knowledge of water quality, fish health, plant care, and aquarium operation—but with some enthusiasm, it's quite manageable! Aquaponics can be forgiving and rewarding, making it accessible to hobbyists at all skill levels.
Incorporation of aquaponics with the home aquarium can provide a unique and rewarding gardening experience and ensure clean water for your aquarium inhabitants, with a salad on the side!
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