It was deemed important to determine whether Tilapia fish green water would allow increased lemon basil plant growth when added to a hydroponic nutrient solution. Since Tilapia effluent is known to contain beneficial microorganisms, it was hypothesized that it would enhance hydroponic plant growth. In the initial study, fish green water was added at varying concentrations (8.3%, 4.2%, and 0%) in three different plastic pool “cultures” (six feet in diameter containing 60 gallons of nutrient solution and 51 culture cups per pool). In the subsequent experiment, the size of the culture containers was decreased in order to obtain additional culture replicates (three replicates in each of the four groups which each contained 19 gallons of nutrient solution and seven culture cups). Nutrient solutions were monitored once a week for pH, temperature, electronic conductivity (EC), and total dissolved solutes (TDS). Also, plants were enumerated and their relative health noted. After eight or nine weeks of culture, the plants were harvested, their relative lengths and masses determined (total, upper plant, and root), as well as the chlorophyll content was enumerated (only in the initial experiment), via a fluorometric technique, for the largest three leaves of each plant. The initial results demonstrated that the 0% green water cultivated plants were significantly greater as compared to the 4.2% green water plants in terms of stem length (p ≤ 0.001), total plant mass (p ≤ 0.001), upper plant mass (p ≤ 0.002) and root mass (p ≤ 0.001). Also, the 8.3% green water cultivated plants were significantly greater as compared to the 4.2% green water total plant mass (p ≤ 0.024) and upper plant mass (p ≤ 0.009). However, the 4.2% green water culture propagated a signifi-cantly greater number of plants as compared to the 0% green water culture (p ≤ 0.040). Thus, the Tilapia effluent seemed to stimulate greater seedling production but then may have depressed the growth of these same seedlings as compared to the 0% green water plants. In the subsequent study, it was determined that the 5.3% green water cultures stimulated a greater number of seedlings per week as compared to all of the other culture conditions: 10.5% (p ≤ 0.001), 2.6% (p ≤ 0.001), and 0% (p ≤ 0.014). In addition, the 10.5% green water culture average weekly seedling value was significantly greater as compared to the 0% culture (p ≤ 0.001). Additional studies will attempt to elucidate the potential reasons for these significant growth differences.
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Vol. 79 • No. 3