Fish Selection for Tank Culture and Feeding Systems

Gary J. BurtleUniversity of Georiga

Animal & Dairy Science Tifton, GA

gburtle@uga.edu229-386-3364

Feeding Indoor Tanks

• Absolutely need a complete feed– Also needs to be digestible

• May supplement with natural food or vitamin-rich products

• Feed every day, or multiple times/day

• Use lighting to grow algae on tank sides

Some Food Items

• Natural foods– Fly larvae, worms, brine shrimp, meal worms

• Ground meat– Beef liver, egg yolk, shrimp, fish paste

• Yeast– Brewers, specialty

• Food waste - vegetable

• Fertilizer – for greenwater or biofloc

Live Food Culture

Brine shrimp for small fish

Aeration and a light source are required.Salt water to hatch cysts.

Artificial Feed for Small Fish

50% protein, small particle, Zeigler

Finfish Feed

Tilapia Fingerlings in TankWith Clear Water

Tilapia Nutrient Requirements

• 25 to 30% protein

• Can use plant materials effectively

• Fiber should be kept low

• Fat should contain linoleic (n-6) fatty acids, about 1% of diet

• A complete vitamin and mineral supplement is needed for tank culture

Bluegill Nutrition Notes

• Natural diets contain about 20% plant material

• Large zooplankton, insects and crustaceans make up most of the diet

• Therefore, bluegill are carnivorous– A relatively high protein (35 to 40%) and high

fat (10 to 15%) diet is recommended

Catfish Nutrient Requirements

• Protein• Fiber• Vitamin C• Other Vitamins• Minerals

• Note: Stock at >8 catfish per cubic foot

• 28 to 36%• > 4%• 80 mg/kg Stable C• Complete (12 items)• P, Zn, Co, Cu, I, Se,

Mg, Fe, Ca

Potential Bluegill Diets

ZieglerZiegler

SilverSilver

RangenRangen

400400

AquamaxAquamax

500500

Silver Silver CupCup

ProteinProtein 4040 4141 4141 4040

FatFat 1010 1212 1212 1212

FiberFiber 44 55 44 --

AshAsh 88 88 1010 --

Bream Growth in Recirculating System, 200 days (7 months)

0

20

40

60

80

100

120

140

160

0 50 100 150 200

BG-M

BG-F

HY-M

HY-F

1/3 lb

Growth of Israeli Hybrid Tilapia(pounds over weeks)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1 9 17 25 34

Lb/fish

1.3 pounds of gainIn 200 days

Tilapia Feeding System

• Green water or small pellet feed for first three months

• Supplement with a 28% protein feed for final 3 months

• Feed conversion is expected to be 1.5 pounds of feed per pound of fish and could be better

Hybrid Tilapia at 800/1200 gal

Green Water Culture

What is Green Water?

• Usually a blue-green algae/water mixture

• Needs open air or greenhouse environment

• Nitrogen and phosphorus provided by feed or fertilization

• Other systems (“green manure”)– Duckweed– Azola water fern

Tilapia in Green Water

• Green water provides a basis for nutrition, usually for smaller stages of fish

• Prepared feed is used to finish the fish later in the growing season– Feed quality and cost can be lowered by the

presence of green water

System Requirements to use Green Water

• Light from the sun or grow lights

• Heat source for the water

• Aerating system

• Sediment collection system

Simple Culture Tank and Sludge Removal Tank

Partitioned System for Catfish/Shrimp and Tilapia

Catfish Area

Tilapia Area

Production from PAS

• Tilapia in two 8 ft compartments of the system (0.33 acres)

• Stocked at 400 to 800 per compartment• Resulted in about 1,000 pounds of Tilapia• Reduced aeration requirement and

improved water quality for catfish/shrimp production (6,000 pounds of catfish)

• Algae was reduced from >100 mg/L to about 50 mg/L by Tilapia (less blue-green)

Exposed Tilapia Tank with High Rate Aeration

BIOFLOC PRODUCTION = BROWN WATER

What is Biofloc?

• Each floc is held together in a loose matrix of mucus that is secreted by bacteria,

• bound by filamentous microorganisms,

• or held by electrostatic attraction.

• also includes animals that are grazers of flocs, such as some zooplankton and nematodes.

• NEEDS A HIGH RATE OF AERATION.

Bacteria, algae, protozoa

The effects of feeding tilapia increasing levels of DUCKWEED. Tilapia were held in static water in concrete tanks (Hassan and Edwards 1992). The fish initially weighed approximately 41g

Feeding rate Lemna Survival rate Mean LW gain Conversion

(g DM/kg fish) of fish (%) (g/d) of Lemna DM

to fish live-

weight (g/g)

10 97 0.2 1.9

20 100 0.4 1.9

30 100 1.0 1.6

40 60 1.0 2.3

50 27 0.7 3.3

60 17 0.8 3.3

Bottom Line

• Use green water to reduce cost

• Stock the fish that you can sell at a good price

• Use supplemental feeds to finish out the fish

• Tilapia still are the best candidate for tank culture as food fish

• But, less regulation of bluegill or catfish.