by Eszter Kun ’22
What is aquaponics?
Aquaponics is a food-producing method that integrates aquaculture with hydroponics (Diver & Rinehart, 2000). In other words, it combines fish breeding with soilless crop production. This method makes it possible to naturally satiate plants’ nutrient requirements and therefore avoid artificial nutrient solutions used in hydroponics. In addition, ammonia, which is a large component of nutrient solutions used in aquaponics, is toxic to the fish and it would poison them if allowed to accumulate within the water supply.
Aquaponics systems are dependent upon the nitrogen cycle, which occurs between the atmosphere and the soil, to make nutrients available to crops (Wongkiew et al., 2017). The system utilizes waste ammonia produced by fish as a byproduct of respiration. Nitrification is a two-step oxidation process: first, AOB-type bacteria convert waste ammonia into nitrites; then, NOB-type bacteria convert those nitrites into nitrates—an available form of nitrogen for plants (United States Environmental Protection Agency, 2002).
What are the main benefits?
Aquaponics is an innovative approach to water management as well as water protection. As the same water is used for raising fish and growing food, according to Nelson and Pade Ict., this technology can provide 8 times more food per acre using 1/6th of the water compared to traditional agriculture, which means about 90% less water is used throughout the whole process. Furthermore, as the biological processes ensure enough nutrients, aquaponics can also protect our rivers and lakes from water pollution by eliminating the use of artificial nutrient solutions, fertilizers, and pesticides (Nichols & Savidov, 2011, May).
Building an aquaponics system that could be used in education
After careful research on aquaponics, I decided to start my own aquaponics project. First, I built an experimental Deep Water Culture (DWC), Non-Recirculating Aquaponics System (1). Then, in order to improve use of the nutrient and water mix, I used a water pump to create a Recirculating (RAS) Closed-Loop-type system (2). While managing the system, I detected meso- and micro-element deficiencies, but found that these deficits can be solved using worm composting. I also discovered that using water circulating systems results in more efficient management and facilitation of growth in plant samples.
Using what I have learned from this initial phase, I created a new system design, which I believe is capable of functioning in education as a teaching tool (3). The basics are similar to the experimental RAS system, and it has the parameters shown below (4). The system’s water tank contains 10 liters of water boiled then cooled to eliminate chlorine. The grow bed is filled with 6 liters of dried clay growing media. In order to achieve a dynamic water recirculation, a 4W, 250 liters/hour water pump is used, which keeps the water level at 70% in the grow bed. Additionally, a LED grow-lamp system was built and installed. The lighting is turned on for 12 hours a day, while the water pump runs continuously. In the system, Endler’s livebearers (Poecilia wingei) fish are bred. Dendrobaena Veneta sp. Composting worms were also introduced to the grow beds.
The success of an aquaponics system depends on certain water quality and plant growth factors. I monitored these factors using JBL Ammonia/Ammonium and JBL EasyTest 6in1 water tests, Parrot Flower Power Bluetooth soils sensors, and EasySense VISION digital data loggers. I measured the values of ammonia, nitrates, and nitrites during the initial 30-day cycling period, when the nitrogen cycle stabilized. Then, I monitored chlorine, pH, general hardness (GH), carbonate hardness (KH), dissolved oxygen (DO), temperature (T), light intensity, and the appearance of solid waste in the water (5). To further demonstrate the educational aspects of aquaponics, I implied the Winkler Titration Method to measure DO, monitored the germination speed of different seeds, and visually detected nutrient deficiencies.
By monitoring these factors in all three of my systems, I was able to create optimal conditions for the bacteria, worms, fish, and plants, which interacted in the way shown in the diagram below (6). I grew common sorrel (Rumex acetosa), Red leaf lettuce (Lactuca sativa var. secalinum), Curly parsley (Petroselinum crispum var. crispum), and Sweet basil (Ocimum basilicum) plants from seeds and seedlings in the working system.
Using the system in education
Using aquaponics systems in education has a lot of potential. The measurements, experiments, and monitoring that take place during the building and managing processes offer new ways of interactive learning through multiple disciplines (Emily et al., 2014).
This system can be used for teaching in two different ways. One is to hold 15-60 minutes presentations with a built-in seminar-style discussion. I held mini-lectures like this at multiple schools and conferences for students from 1-12 grades (7). Every lecture is designed for the appropriate age group in a given time frame. However, generally, each lecture begins with getting to know the definition and the basics of aquaponics, after which we focus on an important scientific concept that connects to aquaponics, such as the nitrogen cycle. All lessons then end with a discussion on water-related and environmental problems and sustainability. As tools, I use my aquaponics system, illustrative representations of it, and an interactive game.
My aquaponics system can also be used in longer learning periods. In these conditions, students can build and manage their own system using the design I have provided for them. They get the opportunity to research the topics, create building plans, and conduct measurements themselves. Each student can choose the parts they are most interested in and work on those, while still working in a group with others. In order to support using my system in longer classes, I provide a detailed system design, financial plan, and additional teaching materials.
Conclusion
I designed and built an aquaponics system that can be sustainably used in classrooms with the following benefits:
- It provides learning opportunities on different levels, from the basics of nitrification to plant nutrition and nutrient transport, and subjects, such as biology, chemistry, physics, and agricultural studies.
- As it is an interactive and enjoyable teaching material, it can also offer solutions to problems in education, like monotony and lack of hands-on experience.
- The introduction to the usually unknown environmental benefits of aquaponics is advantageous, too: aquaponics can increase water awareness among students and even motivate them to innovate projects related to water sustainability of their own.