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 % | |
 |
 |
Nile tilapia harvested from Commercial-scalebiofloc tank |
Red tilapia harvested from Research-scalebiofloc 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 m2.5 cm x 2.5 cm mesh |
60 ft x 60 ft x 10 ft1" x 1" mesh |
 |
 |
Tilapia feeding with floating pellets |
Aeration for the tank with 0.5 hp vertical lift |
|
|
|
Solids removal by passive settlingin cone-bottom tank |
Horizontal circulation with 0.5 hp floating prop |
 |
 |
Base addition tomaintain pH 7.5 |
Netting to hinder access by predatorsespecially 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 |
 |
 |
| Horticulture production of vegetable crops | Production of forage grass |
 |
 |
| Dewatering solid waste with Geotube® | |
|
|
|
| Seedling and crop production with biofloc solid waste | |
 |
 |
| Production of emergent aquatic plants in the denitrifying tanks | |
