A PRELIMINARY COMPARISON OF CLEARWATER RAS AND BIOFLOC- BASED SHRIMP LITOPENAEUS VANNAMEI CULTURE SYSTEMS

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A PRELIMINARY COMPARISON OF
CLEARWATER RAS AND BIOFLOC-
BASED SHRIMP LITOPENAEUS
VANNAMEI CULTURE SYSTEMS
Andrew J. Ray and Jeffrey M. Lotz

Introduction
•Clear water recirculating aquaculture systems (RAS)
–External Filters
•Solids Removal
•Biofilters
•Disinfection
•Biofloc-Based Systems
–Microbial Community
•Internal Biofilter
•Nutrient Recycling (lower FCR)
–External Filters
•Solids Management

Clear Water RAS Versus Biofloc
•Both System Types
–High Level of Biosecurity
–Inland/Indoor Shrimp Farming
–Environmentally Sustainable
•Purpose of this Study
–Preliminary Comparison of Clear Water RAS and
Biofloc Systems
–Evaluate Shrimp Isotope Levels
•Pelleted Diet Only in Clear Water
•Examine Biofloc Nutritional Contribution

Methods
•4, 1.5 m Diameter x 1 m Deep Tanks
•2 Randomly Assigned Treatments
–Clear Water (CW) = 2.75 m3 each
•Bead filter, foam fractionator, moving bed bioreactor,
2 pumps
–Biofloc (BF) = 1.5 m3 each
•Settling chamber, aeration,
oxygenation, sucrose
–Shrimp stocked at 250 m-3
–Partially Reused Water
•Shrimp Fed Based on
Number Stocked

Results
Treatment
CW BF
Temperature (⁰C)
AM
29.9 ± 0.1 (25.5-32.8) 29.6 ± 0.1 (26.7-30.7)
PM 29.2 ± 0.1 (26.7-31.6) 29.6 ± 0.1 (27.1-30.6)
Dissolved Oxygen (mg L-1)
AM 7.5 ± 0.1 (5.8-8.9) 8.2 ± 0.3 (5.5-21.0)
PM 7.5 ± 0.1 (3.5-8.8) 7.4 ± 0.1 (5.0-13.1)
pH
AM 7.8 ± 0.0 (7.1-8.1) 8.1 ± 0.0 (7.5-8.5)
PM 7.7 ± 0.0 (7.1-8.1) 7.8 ± 0.1 (3.9-8.5)
Salinity (‰)
20.4 ± 0.0 (19.4-21.3) 20.6 ± 0.1 (19.3-22.7)
Treatment
CW BF
Ammonia (mg TAN L-1)0.2 ± 0.0 (0.0-0.4) 0.6 ± 0.2 (0.0-1.8)
Nitrite (mg NO2-N L-1)0.1 ± 0.0 (0.0-0.7) 6.1 ± 2.2 (0.0-26.7)
Nitrate (mg NO3-N L-1)96 ± 14 (45-166) 38 ± 12 (0-80)
TSS (mg TSS L-1)105 ± 13 (60-190) 288 ± 50 (185-560)
VSS (mg VSS L-1)20 ± 5 (0-50) 216 ± 51 (80-490)
Alkalinity (mg CaCO3 L-1)87 ± 12 (61-135) 330 ± 61 (128-482)
Turbidity (NTU) 0.7 ± 0.2 (0.1-1.4) 106.8 ± 48.0 (19.1-301.3)
• pH
• TSS?
• Nitrite
• Nitrate
Data are reported as mean ± SE (range)

Results
0
20
40
60
80
100
120
140
160
0
1
2
3
4
5
6
7
mg NO3-N L-1
Week
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
mg TAN L-1
0
5
10
15
20
25
30
mg NO2-N L-1
CW
BF
• Growth rate 0.7 g wk-1
• Survival
- 61% CW
- 43% BF

Isotopes
•Significant differences between shrimp isotope levels
(P ≤ 0.02)
•Δ = fractionation factor
–Subtract from shrimp to make them “look” like their food source
Data are reported as mean ± SE
δ13C∆δ13Cδ13C - ∆ δ15N∆δ15Nδ15N - ∆
CW Shrimp
-21.8 ± 0.1a1.3 9.1 ± 0.0a2.1
BF Shrimp
-20.2 ± 0.1b-21.5 ± 0.1 11.2 ± 0.3b9.1 ± 0.3
Feed -23.1 ± 0.1 7.1 ± 0.5
Biofloc -17.4 ± 0.3 10.6 ± 0.6
• Heavy/Light, compared to a standard
• Light isotopes preferentially excreted = animal tissues are heavier
than food items = fractionation

Biofloc C and N Contributions
•Two Sample Mixing
Model
–Source 1 (f1) = feed
–Source 2 (f2 ) =
biofloc
6
7
8
9
10
11
12
-24 -23 -22 -21 -20 -19 -18 -17
δ15N
δ13C
Feed
Biofloc
Shrimp
f1f2
Carbon 72.3% 27.7%
Nitrogen 41.5% 58.5%
𝑓
1= (𝛿𝑆𝐴𝑀𝑃𝐿𝐸 − 𝛿𝑆𝑂𝑈𝑅𝐶𝐸 2)/(𝛿𝑆𝑂𝑈𝑅𝐶𝐸1− 𝛿𝑆𝑂𝑈𝑅𝐶𝐸 2)
𝑓
2= 1 − 𝑓
1

Summary
•Nitrogen
–Reliable nitrification in
CW  NO3
–↑ NH3 + NO2 in BF, ↓ NO3
•Nutritional contribution
of biofloc
–Incentive to use this
technology
–Overfed BF, underfed
CW?