Whether you found aquaponics through a passion for sustainability, environmental science or personal food production, there really does seem to be something for everyone. I am lucky to work in an environment where people get excited to learn more about what we do. People come through on tours every week who have never heard of aquaponics before, they get so excited when thinking about the possibilities. “So you can grow anything in aquaponics?” Yeah, almost anything. “You can eat the fish too?” Yep, no problem. “This could feed the world!” Sure, in theory…but like so many other things aquaponics is a fairly simple concept with many complex considerations.
Permaculture Design emphasizes designing your environment to utilize energy and resources in the most efficient way possible. Inspired largely by indigenous practices and natural systems, this design science can be applied to landscapes, architecture, food systems, social interactions, business models, governing structures, and on and on. Using a “Niche Analysis”, or needs and yields diagram, helps to illustrate the benefits of aquaponics and why it works as well as its limitations. A niche analysis is very simple; it articulates what each element consumes (needs) and what it produces/contributes back to its’ environment (yields). Understanding the needs and yields of an element will help you identify which ones work best together in order to utilize the energy and resources of each element in the most efficient way possible.
The basic niche analysis for aquaponics includes three ‘elements': fish, plants, and nitrifying bacteria (see attached diagram). According to the niche analysis, you can see a lot of overlap in the needs of the three elements in the chart; all three need oxygen, water, and a specific range in temperature and pH in order to thrive. This tells us why they all can cohabitate in the same environment together…they all have similar needs! But for anyone who is dreaming about building an aquaponics business growing trout and tomatoes – you may want to take another pass at this Niche analysis with more specific needs/yields inputs. Every species of fish and plants will have a specific range of temperature, pH, oxygen levels, etc that they need in order to thrive; and the fact is that many fish and plant combinations simply won’t line up. All fish are not created equally; contrary to my assumptions and early experiments with fish bowls and aquariums as a child, you cannot simply drop any fish into the same tank with water and oxygen and expect that all of them will survive. Study the natural environment the fish species evolved in. Did they come from a pond or a stream? That will tell you about their swimming patterns and therefore what shape tank may be more suitable. What type of climate and geography did they evolve in? That will tell you more about the temperature range they prefer; if your climate and geography differs significantly, that may tell you that you will need to use more energy to heat or cool your space in order to provide the ideal environment. In the tomato/trout farm example, a properly filled out niche analysis would show you that trout prefer temperatures between 50° – 60°F, while tomatoes prefer 65° – 85° F. So unless you plan to chill the water for Trout and then heat it up for the tomatoes within your recirculating water loop, those two will likely not work together. While it is feasible, it would be a highly inefficient use of energy and resources…at least as far as Permaculture Design is concerned.
While the fish and plants often take the spotlight in aquaponics, a smart permaculture designer will recognize the importance of designing for the invisible – the bacteria. In a sense, the nitrifying bacteria are the keystone species of this mini-ecosystem. Without them you have no means of converting the fish waste into a usable form of nitrogen that plants can digest. There are actually two different kinds of naturally occurring bacteria (that’s right, you don’t NEED to purchase any inoculating bacteria kits) that are needed in aquaponics. Nitrosimonas will come first, consuming all the toxic ammonia that the fish produce and yield nitrite as their waste. Since nitrite is still toxic to fish, Nitrospira bacteria come in next to feast on the nitrites and leave behind nitrates as their waste product. Nitrates are a form of nitrogen that plants can easily digest. Designing an aquaponics system outside the needs of the bacteria would make the whole system collapse. In other words, designing a system for plants and fish that need 55°F water would not foster a healthy and productive bacteria community according to the niche analysis temperature needs of the bacteria.
Looking at the needs of these organisms tells us that they can live together, but there are tons of organisms that can live in a temperate, aquatic environment! What makes this combination of elements so productive is that all of the yields of each species fulfills the needs of another. This tells us that the system is not only productive, it is also zero waste! (For example: The carbon dioxide produced by the fish and bacteria is consumed by the plants during the act of photosynthesis, which helps to produce the sugars in carbohydrates that can – in turn – be used to feed your fish…or yourself!) If you were thinking of adding another species into your aquaponics system, it would be beneficial to complete a niche analysis for that species to identify any needs and yields that it produces. You may find out that this new species needs something that you don’t have the capacity to provide in your system, or that it produces too much of something that you can’t use which will throw your system off balance. Speaking of balance, everything within an aquaponics system is a balancing act, from the pH levels to your water temperature and ratios of plants, fish, and bacteria. Turns out it doesn’t take a lot fish to grow a lot of plants! In a completely balanced system the solid fish waste will convert into ammonia as it decomposes which the nitrfying bacteria are happy to consume. As soon as you start to think “I would like to grow more fish in my system,” beware that you’re now talking about throwing your aquaponics system out of balance. Therefore, filtering out a majority of the solid fish waste is a very important consideration for community/commercial scale aquaponics. That solid waste mixture can be used to enrich your compost pile and also makes a great fertilizing soil amendment to your traditional garden.
Although the “meat” of aquaponics as a growing system describes a “closed loop” scenario, most contemporary aquaponics systems are not closed loops. At Flourish Farm, we rely on pelleted fish feed purchased off site, as well as fossil fuel energy to run our fans through the summer, heating elements through the winter, and pumps all year long. There is tremendous work going on all over the world to get these systems closer to going “off-the-grid” with the help of several permaculture patterns and renewable energy techniques. For example, passive solar and walipini greenhouses seek to create off-grid, controlled environment growing spaces by utilizing sun energy and geothermal energy storage. Or – instead of relying solely on natural gas or electric heating elements – using the sun, the earth, even the compost pile to heat water are all possible options depending on your project’s scope and available resources. As a company, we intend to continue to explore these options in future projects, as well as retrofitting existing aquaponics systems as the opportunity arises to keep pushing the boundary of aquaponics and sustainability.