Aquaponics: Hydroponics Meets Aquaculture
By Dr. Joshua Strange, Two Rivers Tribune Contributing Writer
When you grow plants for food, you need to feed the plants nutrients so they will grow well. When you grow fish for food, you need to remove their nutrient rich wastes so they will grow well. Aquaponics takes these two problems and combines them to form a common solution: use the wastes from growing fish to feed plants, which in turn clean the water so fish can thrive. Innovative solutions that turn wastes into valuable resources are a hallmark of sustainability.
Global population recently surpassed seven billion people, and increasing numbers of people fall ill from consumption of unhealthy food products. Besides the epidemic rates of heart disease, obesity, and diabetes, experts are also concerned about increasing global food production to feed the growing human population. As the affluence of a population grows, along with their consumption of mainstream media and advertising, the demand for animal protein typically grows too.
Unfortunately, the moral and environmental costs of factory farming livestock for meat are nauseating. And of course it’s not just about having food to eat, it’s also about having access to tasty, healthy food that is affordable.
A highly touted solution to this global problem is fish farming, also known as aquaculture. Proponents of aquaculture claim that farm raised fish can meet the growing global demands for animal protein. American politicians have shown strong support for fish farming with the National Oceanic and Atmospheric Administration (NOAA) Fisheries launching a massive new aquaculture initiative in 2011.
Advocates say aquaculture can grow healthy fish with little impact on the environment and reduce pressure on wild fish stocks. But, there can be many serious environmental problems with such aquaculture operations. Non-native fish stocks are often used that can wreak havoc when they escape into the wild. Also, fish are typically raised in open-loop systems in high density net pens, requiring the use of antibiotics, pesticides, and fish food typically made from other fish. The resulting concentration of wastes, pollutants, and parasites can cause serious harm to the surrounding environment.
Farmed raised Atlantic salmon are a classic example. In British Columbia, non-native Atlantic salmon are raised in protected ocean inlets where the resulting super-concentrations of parasitic sea lice have infected wild Pacific salmon smolts migrating to the open ocean, resulting in high morality rates. In recent months, a deadly salmon virus from Europe, known as infectious salmon anemia, has escaped into British Columbian waters and is infecting wild Pacific salmon for the first time ever.
Further, Atlantic salmon have been observed spawning in British Columbia rivers and streams, raising fears of unintended ecological consequences. Such consequences could be even greater if the first genetically engineered fish clears the final hurdles for public consumption as is being attempted by the USDA.
Called the AquAdvantgae, this Franken fish is modified with eel pout genes to make it grow all year long. Genetic pollution aside, farmed raised salmon do not have the same levels of super-nutritious omega-3 fats as their wild counterparts and their pale white flesh is dyed red in order make it to look like salmon.
One partial solution to these problems is to have land-based closed-loop aquaculture system where in fish can’t escape, such as is done with catfish farming in the Southwest. Yet this still does not solve the problem of taking clean water and tainting it with highly concentrated fish wastes that are a nuisance to dispose of. Hydroponics has a similar problem and typically uses manufactured chemical nutrients.
In Aquaponics, plants recycle the nutrient rich wastes from fish in a closed-loop system that recirculates the water. This serves to conserve water but also prevents fish and any parasites or disease from escaping into the environment. Thus a closed-loop aquaponic system solves almost all of the environmental problems with both hydroponics and aquaculture.
The two remaining potential problems—food for fish and electricity for pumps can also be solved. Renewable electricity such as solar can power pumps and many fish species, such as the popular tilapia which can be fed vegetable matter such as ground veggies or duckweed, the latter of which has better protein than soybeans. Composting systems can also be used to grow fish food in the form of red worms or black soldier fly larvae, and hanging a light over the fish tank at night can attract a free lunch for your fish.
Young starter fish can be purchased through mail-order fish hatcheries. The California Department of Fish and Game website has a list of authorized fish suppliers in California and relevant information on regulations and best-use practices.
Cold water fish include catfish, trout, bass, and lake perch. In a closed loop-system, no live fish should be escaping but it’s always important to think of the consequences of a potentially invasive species escaping into the wild. Warm water fish such a tilapia, an African cichlid, has an advantage in our area in that it cannot tolerate our cold winters in the wild and therefore cannot become invasive.
Having a successful aquaponics system requires balance between the plants and the fish. A good rule of thumb to keep a one-to-one ratio of the volume of plant grow beds to fish tanks with fish stocking densities at one fish per two gallons of water. As long as balance is kept then an aquaponics systems can be very large but generally no smaller than 250 gallons in order to provide water quality stability for the fish. When setting up a new system, the vegetables are planted first after the pump and water is running and given an initial boost with seaweed extract. Next, young fish are added and fed daily. And you don’t need to worry about weeding as there won’t be any weeds since soil isn’t used.
Grow beds should be one foot deep and are typically filled with a clay-based Hydroton, crushed shale, or pea gravel. Often grow beds are stacked or built on top of the fish tank. One pump can be used to pump the water from the fish tank into the grow beds, which then drains back to the fish tank by gravity.
Manufactured tanks and kits are available for purchase but backyard do-it-yourselfers can build simple lumber boxes covered with pond liner. Often set up in greenhouses, aquaponic systems can be heated depending on climate and whether warm or cold water fish are being grown.
Aquarium heaters can be used to keep water warm but compost heaps or windrows can also be placed in the greenhouse alongside the fish tank to help keep things warm from the heat of decomposition.
This type of system is used by Growing Power, an urban farming outfit in Milwaukee, Wisconsin, to grow fish and veggies even through their frigid winters. Run by former NBA baller Will Allen, this award winning farm annually produces over one million pounds of vegetables, 10,000 table ready fish, and 400 yards of worm compost on only three acres of greenhouses. That’s right, on only 3 acres.
Growing Power has done this feat in an impoverished area that was lacking jobs and access to healthy food. This kind of eye-opening food production highlights the benefits of using aquaponic in city settings to feed the urban masses. Since it doesn’t require soil, aquaponic systems can be used successfully on brownfields and other abandoned areas where the soil is polluted such as old industrial sites or mill yards.
Running a commercial farm operation as a profitable business is always a challenge but these systems are highly attractive to people who want to grow their own food in their backyard, or rooftops, especially year-round.
Besides the tasty healthy food, just think how much fun the kids will have.