The UVI Aquaculture Program has developed a Biofloc System which produces 6,000 lbs of tilapia per six-month crop using biologically active and suspended solids as the primary waste treatment process. Aeration, settleable solids removal, pH adjustments and anaerobic denitrification are additional management practices which allow high yields.

Production parameters SI units USCS units
Production biomass 15.3 kg/m3 0.13 lbs/gallon
Stocking density 25 ea/m3 9.5 ea/100 gallon
Initial size 70 g 0.15 lbs
Final size 707 g 1.6 lbs
Culture period 182 days
Feed Conversion Ratio 1.8
Survival 86 %

   

Harvest from commercial biofloc tank Red tilapia harvest from biofloc tank
Nile tilapia harvested from Commercial-scale

biofloc tank
Red tilapia harvested from Research-scale

biofloc tank

System description SI units USCS units
Rearing tank dimensions 16 m x 1.22 m 52.5 ft x 4 ft
                      volume 200 m3 52,834 gal
                      liner 20 mil HDPE
Aeration - vertical lift  0.5 hp x 3
Circulation - horizontal 0.5 hp x 1
Solids removal - passive settling 1.9 m3 500 gal
                           pump 0.33 hp
                           geotube
Base addition
Denitrifying - dimensions 15.2 m x 1.2 m x 0.4 m 50 ft x 4 ft x 1.33 ft
                      volume 7.3 m3 1,928 gal
Anit-bird net
18.3 m x 18.3 m x 3.0 m
2.5 cm x 2.5 cm mesh
60 ft x 60 ft x 10 ft
1" x 1" mesh
Tilapia feeding with floating pellets Aerator for the biofloc tank
Tilapia feeding with floating pellets
Aeration for the tank with 0.5 hp vertical lift
Solids removal by passive settling
Horizontal circulation
Solids removal by passive settling
in cone-bottom tank
Horizontal circulation with 0.5 hp floating prop 
Base addition to maintain pH 7.5 Anti-bird net to hinder access by preditors
Base addition to
maintain pH 7.5
Netting to hinder access by predators
especially herons, egrets, and pelicans
Operation protocol
Feeding Feed twice daily, ad libitum to apparent satiation for 30 minutes
Feed Complete diet for omnivores, floating pellets, 32% protein, 3% fat, 
Aeration 1 vertical lift initially, then add as needed as biomass increases
Circulation 1 horizontal throughout the production period
Solids removal Pump continuously from the rearing tank to the passive settling tank.  Remove solids twice daily.
Solids dewatering Geotextile bag separates solids from the liquid.  Solids are retained in the bag and liquid is returned to the rearing tank.
Base addition As needed when pH < 7.5
Base  Calcium hydroxide Ca(OH)2
Denitrifying One exchange per day to allow solid settling and buildup of anaerobic zones.
Auxillary activities
Horticultural production of vegetable crops
Adjacent fields are irrigated with filtered system water.
Dewatering of waste
Dried fish fecal waste is incorporated into the soil as a slow-release fertilizer.

Dried fish fecal waste is incorporated into soilless mix for greenhouse seedling production
Production of emergent aquatic plants Aquatic plants are produced in the denitrifying tank

Vegetable production with biofloc effluent Forage grass production with biofloc effluent
Horticulture production of vegetable crops Production of forage grass
Geotube full of sludge Geotube draining filtered water
Dewatering solid waste with Geotube®

Seedlings grown in biofloc solids mix 

 Potted basil seedlings in biofloc solids mix    Cucumbers produced with biofloc solids incorporated into the soil
Seedling and crop production with biofloc solid waste
Taro transplants in biofloc denitrifying tank Taro production in biofloc denitrifying tank
Production of emergent aquatic plants in the denitrifying tanks