HS1252 A Practical Guide for Aquaponics as an Alternative Enterprise1 Richard V. Tyson and Eric H. Simonne2 Florida agriculture lost 25% of its land use in the last 30 years with a significant portion taken out of production by government buyouts enforcing environmental regulations for the purpose of reducing phosphorus and nitrogen discharges to lakes, rivers, springs, and wetlands. Producing crops aquaponically can reduce leaching, runoff, and water discharges to the environment by reusing nutrient effluent from aquaculture and hydroponic systems. Designing and managing agricultural production systems for minimal discharge of water and nutrients to the environment protects groundwater quality, makes agricultural water Figure 1. Aquaponic media filled bench bed (left) floating raft permitting easier to obtain, and will help maintain the long- system (right) and recirculating tanks and filters (top) at Green Acre term sustainability of agricultural enterprises. These designs Aquaponics, Brooksville, FL. also will reduce concerns about discharge of nutrients into Credits: Green Acre Aquaponics coastal zones that could contribute to harmful algal blooms. Choosing the Fish and Plants Aquaponics is an intensive sustainable agricultural produc- Three organisms are involved in the optimum performance tion system that connects hydroponic and aquaculture of aquaponic systems (Table 1). The plants and fish are systems to produce multiple cash crops with reduced the cash crops, while nitrifying bacteria play an important water and fertilizer inputs. It is highly suited for small biofiltration role, converting toxic fish waste ammonia farm producers targeting local markets and agritourism (Francis-Floyd et al. 2012) to nitrate nitrogen (Figure 2), opportunities (Figure 1). one of the most important mineral nutrients required by plants. 1. This document is HS1252, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date September 2014. Revised December 2017. Visit the EDIS website at http://edis.ifas.ufl.edu. 2. Richard V. Tyson, county Extension director and Extension agent IV, UF/IFAS Extension Orange County; and Eric H. Simonne, professor, Horticultural Sciences, and District Director; UF/IFAS Extension, Gainesville, FL 32611. The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office. U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension. systems while plants that prefer well-watered, continuously moist soil (most leafy salad crops and herbs) adapt well to either water culture or media systems (Table 3). Production Methods The most common aquaculture system used in aquaponics is the recirculating aquaculture tank system (RAS). This tank becomes the base nutrient and water reservoir that flows to the hydroponic subsystem and is usually recircu- lated back to the tank. This is an intensive, usually high- fish-density production system (Timmons et al. 2002) that allows for buildup of waste nutrients from fish feed to levels Figure 2. Simplified nitrogen cycle in an aquaponic system that includes plants, fish, and nitrifying bacteria. (TAN = total ammonia that can benefit plant growth. Pond water may contain + + - nitrogen, NH4 = ammonium, NH3 = ammonia, H = hydrogen ion, NO3 harmful microorganisms and algae, so the use of well water = nitrate) or municipal water sources when using RAS aquaponics is recommended. The choices of fish and aquatic organisms have an The most common hydroponic systems (Tyson et al. economic, environmental, and legal component (see the 2013) currently being used in aquaponics are the floating regulations section below). For example, tilapia is one of raft, nutrient film technique (NFT), and the bench bed the most common aquacultured fish due to its tolerance of hydroponic systems (Table 3). Floating raft systems are a wide range of water quality conditions (Lim and Webster ideally suited for quick-turnaround lettuce crops. Many 2006), its favorable feed conversion ratio (1.5–3 pounds of commercially available NFT systems can handle only feed/pound of fish [Chapman 2012]) and its fast growth small-rooted crops like lettuce because of limited trough under warm conditions (market size in 6–12 months). It volume (4 in. wide x 2 in. deep). Large-rooted vegetables fits well when grown with warm-season vegetable crops such as tomato, cucumber, pepper, and mint can be grown like tomatoes, peppers, or cucumbers (Table 2). Tilapia has with NFT provided the trough’s root-zone space is large high-quality, textured white fillets, which present well at enough (18 in. wide x 4 in. deep) to accommodate the plant restaurants. Worldwide, tilapia farming is expanding at a roots and allow water to continue flowing down the trough. rate of 12% to 15% annually. However, tilapia are sensitive Properly designed and operated media (perlite, vermiculite, to low temperatures and stop feeding at 60°F, with lethal peat, coconut coir, pine bark, pebbles, and combinations) temperatures beginning at 50°F and below. Also, inexpen- systems, such as the bench bed, have the broadest crop sive foreign imports depress wholesale prices, resulting in choices because they can accommodate water-loving plants the need for farmers to seek marketing outlets that cater or plants that need well-drained soils. Often, media-filled to the local production of food or live fish markets where plastic pots are placed in the bench bed to facilitate crop higher prices could be expected. Other fish suitable to cycles and make the beds easier to clean and maintain. aquaponics but requiring more stringent water-quality conditions are channel catfish, koi, and other ornamental Water Source and Quality and bait fish. Malaysian prawn and red claw crayfish also have been used in aquaponic systems, but because they Considerations are non-native species their use in Florida is restricted Theoretically, almost any type of vegetable production (Knickerbocker 2013). system could be linked to an aquaculture system. However, linking pond aquaculture to hydroponics unnecessarily High-value vegetable crops that are commonly grown in introduces potentially harmful microorganisms and algae hydroponic systems such as tomato, cucumber, pepper, to the aquaponic system, which could adversely affect the lettuce, and mixed herbs are recommended for successful fish and plants. Thus it is recommended to use well water commercial aquaponic production (Tyson et al. 2013). or municipal water sources when using RAS aquapon- However, matching the right plant to the right hydroponic ics. Municipal water sources contain chlorine and/or system is an important decision. All plants can be grown chloramines, which are very toxic to fish and can kill them hydroponically, but to maximize yields, plants that grow when present in very low concentrations. To minimize best in drier, well drained soils do best in media hydroponic the risk of chlorine exposure, municipal water should be A Practical Guide for Aquaponics as an Alternative Enterprise 2 aerated in a separate tank for a few days before placing in pH increases from 6.5 to 8.5 (Tyson et al. 2008), utilizing the aquaculture tank. Ideally, water should be tested for the the NH3 as the beginning substrate in the reaction. Thus presence of chlorine before it is allowed to come in contact growers should consider the balance between pH and toxic with the fish. ammonia verses the sustainability factor of driving the biological production of nitrate nitrogen. If the aquaponic Determining the best production methods to use can be system is balanced with ammonia levels between 0 to 1.0 complicated by the various optimum temperatures and ppm (1 ppm = 1 mg/L), pH could range between 6.5 and pH for maximum growth and yield of the three major 7.5, with 6.5 more advantageous for the plant when TAN is organisms necessary for successful operations (Table 2). 0 and nitrification more advantageous for the system from This often results in a compromise, depending on which a sustainability point of view driving nitrate production plant and fish you choose to produce. A good starting point when the TAN is 1.0 ppm. Tanks experiencing consistently for warm-season vegetables, tropical fish, and nitrifying higher ammonia levels >2.0 ppm may want to reduce pH bacteria would be to keep the water pH between 6.5 and to lower the toxic concentration of NH3, thereby reducing 7.5. Plant uptake of certain nutrients is better at pH 6.5. stress on the fish. In addition, stop feeding and begin water Nitrification rate increases at pH 7.5, speeding the reaction replacement to return TAN to safe levels before considering which turns toxic ammonia (NH3) into nitrate nitrogen production at higher pH levels. (NO3-), the preferred nitrogen source for plants. At pH 7.5, micronutrient deficiency in plants (primarily iron Besides regular measurements of pH and TAN, oxygen and manganese) may occur but can be overcome by foliar measurements also should be taken periodically. The nutritional sprays of the deficient nutrients. Many factors most common causes of fish mortality are prolonged high can influence system water pH, including: ammonia (>2 ppm) and low oxygen (<3 ppm) levels. These conditions can be made worse if high fish densities and feed • Nitrification produces hydrogen ions and consumes levels are maintained.