Comparison of Different Light Technologies for Indoor Aquaponic Production of WhiteStemmed Pak Choi Brassica rapa

To develop aquaponic systems for urban environments or northern latitudes, they will need to be located indoors in insulated buildings necessitating the use of artificial lights. Fluorescent and metal halide grow lights are widely used in hydroponics. More recently, light emitting diodes (LEDs) have become widely available. Another technology receiving increased interest is induction lighting. To date, these lighting technologies have not been compared for their application to indoor aquaponics. The objective of this research was to compare different artificial lighting technologies on plant growth. Each of the four replicate systems included a 415-L fish tank, a 190-L settling tank, a 115-L clarifier, and two 1.5 m2 floating raft beds. Tilapia of 100 g average weight were stocked in the culture tanks at 32 fish/m3. White-stemmed pak choi (Brassica rapa var. chinensis) seedlings where suspended in floating rafts at 16 seedlings per raft. There were four different types of lights evaluated, including: 1) metal halide; 2) fluorescent; 3) induction, and 4) light emitting diode (LED). The trial utilized a Randomized Complete Block Design over the four replicate systems. There were four replicates of each type of light, blocked by bed. Fish were fed a floating 32% protein commercial fish feed twice daily according to a feed chart. The duration of the experiment was four weeks. At harvest, the four plants in the center of each raft were separated into roots and leaves, then measured and weighed. Light effects were compared based on plant weights and “root to shoot” ratios. Average fresh weight of pak choi raised under light emitting diode lights (LED) (400 g) were significantly greater (P ≤ 0.05) than weights of plants raised under florescent (87 g), induction (130 g), or metal halide lights (94 g). Similarly, the root:shoot ratios of pak choi plants raised under light emitting diode lights (LED) were significantly greater than ratios for plants raised under the other light types. Results indicated superior performance by LED for pak choi production in indoor aquaponics