The effects of different densities of caged Nile tilapia, Oreochromis niloticus, on water quality, phytoplankton populations, prawn, and total pond production were evaluated in freshwater prawn, Macrobrachium rosenbergii, production ponds. The experiment consisted of three treatments with three 0.04‐ha replicates each. All ponds were stocked with graded, nursed juvenile prawn (0.9 ± 0.6 g) at 69,000/ha. Control (CTL) ponds contained only prawns. Low‐density polyculture (LDP) ponds also contained two cages (1 m3; 100 fish/cage) of monosex male tilapia (115.6 ± 22 g), and high‐density polyculture (HDP) ponds had four cages. Total culture period was 106 d for tilapia and 114 d for prawn. Overall mean afternoon pH level was significantly lower (P ≤ 0.05) in polyculture ponds than in CTL ponds but did not differ (P > 0.05) between LDP and HDP. Phytoplankton biovolume was reduced in polyculture treatments. Tilapia in the LDP treatment had significantly higher (P ≤ 0.05) harvest weights than in the HDP treatment. Prawn weights were higher (P ≤ 0.05) in polyculture than prawn monoculture. These data indicate that a caged tilapia/freshwater prawn polyculture system may provide pH control while maximizing pond resources in temperate areas.

Aquaponics is an integrated fish and plant recirculating production system. The University of the Virgin Islands' raft aquaponic system uses a cylindro-conical clarifier as a primary solids removal device; however, a swirl separator may offer advantages. The objectives of the 8-wk experiment were to compare water quality parameters, Nile tilapia, Oreochromis niloticus, production and water spinach, Ipomoea aquatica, production in a raft aquaponic system using a clarifier or swirl separator for primary treatment of solids in the waste stream.No significant differences (P ≥ 0.05) existed between treatments for temperature, oxygen, pH, total suspended solids, alkalinity, electrical conductivity, total ammonia-nitrogen, nitrite-nitrogen, nitrate-nitrogen, macronutrients, and micronutrients concentrations in the culture water. There were no significant differences (P ≥ 0.05) between treatments for Nile tilapia production, average weight, survival, or feed conversion ratio. There were no significant differences (P ≥ 0.05) between treatments for water spinach production or plant tissue analysis. In conclusion, the swirl separator used in this experiment performed similar to the clarifier and water spinach grew vigorously in the raft aquaponic system.

Aquaponics is an integrated fish and plant recirculating production system. Solid fish waste must be removed from the production system to maintain optimal water quality parameters for fish and plant health. The University of the Virgin Islands (UVI) raft aquaponic system's primary treatment device for solids removal is a cylindro-conical clarifier; however, alternative mechanical filtration devices such as a parabolic screen filter (PSF) may offer advantages. The objectives of the elevenweek experiment were to compare water quality parameters, Nile tilapia (Oreochromis niloticus) production and water spinach (Ipomoea aquatica) production in a raft aquaponic system using either a cylindroconical clarifier or parabolic screen filter for primary treatment of solids in the waste stream. Effect of Screen Filter on Production of Tilapia and SpinachInternational Journal of Recirculating Aquaculture 12 (2011) The water quality results showed no significant differences (P > 0.05) between treatments for temperature, oxygen, pH, alkalinity, EC, TAN, NO 2 -N and NO 3 -N, macronutrients and micronutrients concentrations, with the exception of copper and zinc. There was no significant difference (P > 0.05) between treatments for the total suspended solids (TSS) concentration entering either primary filtration device; however, there was a significant difference (P ≤ 0.05) between treatments for TSS concentrations exiting the primary filtration device. The PSF treatment had a significantly higher (P ≤ 0.05) TSS concentration exiting the unit and a significantly higher (P ≤ 0.05) TSS concentration in the secondary treatment device (net tank) compared to the clarifier.There were no significant differences (P > 0.05) between treatments for Nile tilapia production, average weight, survival, or feed conversion ratio. There were no significant differences (P > 0.05) in water spinach production or plant tissue analysis between treatments. In conclusion, the PSF used in this experiment performed less effectively in removing TSS compared to the clarifier, would require more labor to clean and would not be recommended for use in a larger raft aquaponic system. In addition, water spinach assimilated dissolved fish wastes well and grew vigorously in the raft aquaponic system.

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Integration of intensive aquaculture systems with greenhouse plant production has been shown to improve aquaculture water quality conditions and improve plant nutrient use efficiency. The majority of the focus of integrated systems has involved raft culture or true hydroponics. Little work has been done on soilless culture utilizing drip irrigation. This study investigates the feasibility of integrating biofloc Nile tilapia (Oreochromis niloticus) production with greenhouse cherry tomato production (Solanum lycopersicum var. cerasiforme). Nile tilapia (157 g/fish) were stocked at 40 fish/m3 and grown for 149 days. The cherry tomato cvs. “Favorita” and “Goldita” were grown with aquaculture effluent (AE) waste and compared to plants grown with conventional fertilizer (CF) in soilless culture. Plants were grown for 157 days. Few differences in yield occurred between treatments until fish harvest (117 DAT). Post fish harvest, there was an 18.4% difference in total yield between CF and AE at crop termination for “Favorita”. Differences in yield between AE and CF were observed for “Goldita” at fish harvest (117 DAT) and crop termination (157 DAT). Results from this study suggest the potential for successful integration of cherry tomato grown in a substrate-based system with AE from a tilapia biofloc production system.