Evaluation of an Aquaponics System

Aquaponics is an agricultural system which symbiotically combines aquaculture and hydroponics in a recirculating, closed-loop system.   Nitrifying bacteria, once established, convert fish waste into plant fertilizer for hydroponic plant growth, while simultaneously acting as a biofilter for aquaculture.  The objectives of this research included evaluation of water quality and plant health in an aquaponics system.  To achieve this, an aquaponics system was designed, constructed, and implemented with a media-filled-bed (MFB).  The system was designed to be low-cost, easily assembled from readily available components, and modular.  Once designed, constructed, and placed into operation, the aquaponics system was maintained over nine months with water quality parameters and plant growth data recorded.  This nine month period consisted of two phases: 1) initial system cycling, maturation, and viability assessment; and 2) plant health and growth evaluation.  During phase one titration tests were regularly conducted to measure fluctuations in pH, ammonia, nitrite, and nitrate levels.  The goal of these tests were to determine whether the system had “cycled,” defined by the effective microbial conversion of fish waste by-products (ammonia) into nitrates for plants.  During phase two, a variety of plants were transplanted into the system and observed over a four-month period.  The plants were photographed and measured at weekly intervals and titration tests were conducted for pH, nitrates, and ammonia.  Nitrate, nitrite, ammonium, and pH data will be presented.  Plants were observed for nutrient deficiencies and pest populations.  The system was able to produce vigorous plant growth in varieties with high nitrogen demand due to consistently high levels of nitrates.  However, overall plant health varied due to observed deficiencies in other nutrients, such as potassium and iron.  It was concluded after phases one and two, that the aquaponics system, as designed and constructed, was a viable agricultural technology with certain important limitations.