If you are reading this, chances are you enjoy raising plants. The joy of growing your own beautiful flowers and nutrient-rich vegetables is undeniable. Gardening has immeasurable benefits for the mind, body and soul that people have been enjoying for generations. Now, with the recent push for locally grown produce, growers are finding that their passion for plants can be profitable as well. Aquaponics is an affordable, sustainable and rewarding way to grow your own delicious, protein-rich fish in harmony with your plants. With aquaponics, you can grow your own plants and fish in the same system with controlled environment agriculture techniques.
Hydroponics is the growing of plants without soil in a nutrient solution. Aquaculture is fish farming. Aquaponics is a combination of these two growing methods. Aquaponics takes advantage of the symbiotic relationship between certain crops and fish and provides a sustainable means of growing a lot of food in a small footprint. In a hydroponic system, the pH and fertilizer levels need to be monitored. With aquaponics, there are just a few other water parameters that need to be measured. These include dissolved oxygen, ammonia, nitrite and nitrate levels.
Aquaponics is quite simple. Fish produce a nutrient-rich waste that is absorbed by the plants. The plants help to filter the soiled water before it goes back to the fish. It’s a constant cycle. Getting into the details, the fish produce waste containing nutrients and relatively high levels of ammonia. This waste then goes through what is called a bio-filtration process. In this process, there are good microbes hard at work that converts the fish waste into fertilizer for the plants. They work to convert the ammonia into nitrite, and the nitrite into nitrate. Once the bio-filtration process is complete, the nitrate-rich water is delivered to the plants. The plant’s roots then help to clean the water before it goes back to the fish.
Plants can be grown in a raft or float bed, but some people will grow their plants in a media bed of pebbles or expanded clay. Media beds are a good way to grow but require a little more maintenance. The media will need to be removed, at least annually, for cleaning, which is not necessary in a raft or float bed system. Fish are usually kept in stock tanks, troughs or ponds. The symbiotic relationship between fish and plants is highly sustainable with relatively low inputs. Growing fish locally helps reduce the burden on the global fish market, is a rewarding way to grow protein and can even be certified organic.
In most circumstances it takes about forty days to get the bio-filtration process working properly. The process of getting a system up and running is called cycling. It allows the good microbes to be built up to sufficient numbers to convert the fish waste into fertilizer for the plants. The ultimate goal is to have no ammonia or nitrites in the water and only nitrates present. High levels of ammonia and nitrite can kill fish.
The cycling process should be started before fish are introduced to the system. This involves pumping water throughout the system and monitoring the pH, dissolved oxygen and microbe population. Once the water reaches homeostasis, the ammonia and nitrite levels need to be checked at least daily. After the cycling process is complete, these parameters should only need to be tested weekly. As the bio-filter gets going, the ammonia levels will rise. After about 10 days, the ammonia will start to decline and the nitrite levels will start rising. Then in about 30 days, the nitrite level will start to decline and the nitrate levels will begin increasing. This is the goal and patience is crucial during cycling.
This process will occur naturally over time but one trick to get a jump-start on the cycling/bio-filtration process is to obtain some “seasoned” water from a trusted source. The best source is from an already functioning aquaponics system. Seasoned water will have the essential microbes already growing in it, cutting down on cycling time substantially. Once the microbes are in the system, they need food. The microbes eat ammonia, so in conjunction with introducing seasoned water, ammonia also needs to be added. An over-the-counter product will work to feed the good bacteria as long as it is straight ammonia and has no additives.
There are many types of fish that grow well in an aquaponics system. It is recommended to choose a type of fish that grows easily for the first attempt. Tilapia is a very popular fish for aquaponics. They are a hardy fish and will tolerate a high stocking density with no cannibalism, as well as a wide variety of water parameters that some fish will not handle. They are very forgiving and are a good option to “get your feet wet” in aquaponics. Tilapia also has a great food conversion rate. For each pound of food given to the fish, they will gain one pound of weight. This 1:1 food conversion rate is almost unheard of in nature. Chickens, for instance, take two pounds of food to make one pound of meat and hogs take about three pounds. Other types of fish that grow well in aquaponic culture are trout, perch and bass, but these are much more challenging due to the very high quality of water and dissolved oxygen levels that they need.
The inputs that are required for an aquaponics system are the fish, fish food, energy to run your pump and aeration system and water. The outputs are fish, vegetables and/or flowers. The ecological benefits include reducing your carbon footprint and becoming self sufficient in your food production. Locally grown produce truly is 1,000 times fresher; much of what is available in the grocery store has traveled a great distance to get to the shelf. The plants grown in an aquaponics system will generate most of the income. The fish just eliminate the need for fertilizer and drive the system. When sizing an aquaponic system it’s important to keep in mind the chemistry of the water. The more water in a system, the fewer fluctuations there will be in its chemistry.
Aquaponics is gaining popularity by the day. Locally grown food is safer, healthier and more environmentally friendly than food imported from foreign markets. Whether you are growing for your family or farmers’ market, the symbiotic relationship of fish and plants is something you should consider in your growing operation.
Sam Shroyer has a bachelor’s degree in horticulture from South Dakota State University and 20 years of horticultural experience, it is his goal to “re-teach” the public that sustainability and self-sufficiency is well within everyone’s reach.