الفهرس 
biofloc technology and minimization of water usageOnly 14 pages are availabe for public view
Abstract
The present study was carried out in the hatchery lab of Fish Production Branch, Department of Animal Production, Faculty of Agriculture, Ain Shams University. The aim of the study was to evaluate the effects of three different carbon sources: molasses (T1), vinasse (T2) and cornstarch (T3); on microbial activity, water quality parameters and growth performance of Orechromis niloticus in indoor biofloc tanks compared with that reared in a clear water with no carbon sources (T4). The present study was performed in two parallel experiments with a joint control treatment. The first experiment was to compare cornstarch with molasses at C: N ratio 20:1. The second experiment was to test the vinasse as cheaper carbon source at C: N ratio 10:1. The microbial activity, water quality and growth performance parameters were used to evaluate the effect of different carbon source.
Experiment I
The results obtained from the first experiment could be summarized as follows:
1. Total ammonium nitrogen.
Molasses groups gave the highest average of Total ammonium nitrogen 4.79 mg l-1 while the lowest value was obtained by control group1.45 mg l-1. The statistical analysis of total ammonium nitrogen showed that there was a significantly difference between molasses and control treatment (P<0.05). However there was no significant difference between molasses and cornstarch treatments (P>0.05).
2.Nitrite The highest total average level of nitrite was recorded in molasses treatment (4.49 μg L-1) while the lowest nitrite level was recorded in the control group (1.12 μg L-1). There were statistical significant differences between all treated groups in nitrite levels at (P<0.05).
3. Nitrate
The highest total average of nitrate level was recorded in the control group (158.27μg L-1) while the lowest nitrite level was recorded in molasses treatment (14.86 μg L-1). There were statistical significant differences between molasses, corn starch and control groups in nitrate levels at (P<0.05).
4. pH
Molasses group yielded the highest value of negative logarithmic of hydrogen ion concentration (7.09) and the lowest value was recorded in control group (6.52) there were a significantly differences between molasses and control (P<0.05) but there were no significantly differences between molasses and corn starch (P<0.05).
5. Total suspended solids and volatile suspended solids
The highest values of total and volatile suspended solids were recorded in the cornstarch treatment, while the lowest recorded values were in the control treatment. The statistical analysis showed that there was no significant difference in total suspended solids and volatile suspended solids between molasses and corn starch treatments (P<0.05). There were significant differences between molasses, corn starch and control group (P<0.05) 6. Floc volume index and total bacterial count.
The highest floc volume index (FVI) and total heterotrophic bacteria (THB) were recorded in molasses treatment; whilst the lowest concentration was recorded in cornstarch treatment. All readings of floc volume index equal zero in control treatment, where no carbon sourece was added. No significant difference between molasses and cornstarch treatments was recorded (P<0.05).
7. Fish survival rate
The survival rates in a control and all treated groups were around 98 %, there were no significantly differences between all treatments (P>0.05).
8. Proximate composition of biofloc and fish
Molasses treatment yielded the highest value of fish crude protein, which was significantly higher at (P<0.05) than that of the cornstarch and control groups. The control group recorded the lowest fish crude protein content. The highest value of fish ether extract was obtained in the corn starch group, it was significantly higher (P<0.05) than that of the molasses and control treatments, which recorded the lowest ether extract contents. The highest value of ash was noticed in corn starch treatment which was significantly (P<0.05) higher than that of the molasses and control. The highest value of biofloc protein content was recorded in molasses, which was significantly higher at (P<0.05) than cornstarch treatment. The highest value of biofloc ether extract was recorded in cornstarch, which was significantly higher at (P<0.05) than molasses treatment. The highest value of biofloc ash was recorded in corn starch treatment, which was significantly higher at (P<0.05) than molasses treatment.
9. Body weights and growth performance Molasses treatment yielded the highest values of fish growth parameters (Total Weight Gain (TWG), Specific Growth Rate (SGR), Net yield, Final body weight) and nutritional parameters (Feed Conversion Ratio (FCR), Protein Efficiency Ratio (PER) and Net Protein Utilization (NPUa)). While the lowest values of fish growth parameters were recorded in control group. The statistical analysis showed that there were significant differences in growth and nutritional parameters among molasses and corn starch and control treatments (P<0.05), but there was no significant difference (P<0.05) between cornstarch and control treatment.
Experiment II
1. Total ammonium nitrogen.
The highest total ammonium nitrogen level was recorded in vinasse treatment (7.39 mg L-1) while the lowest level was recorded in control treatment (1.45 mg L-1). There were significant differences between vinasse and control (P<0.05).
2. Nitrite
The highest concentration of nitrite was recorded in control treatment (1.13 μg L-1) while the lowest concentration was recorded in vinasse (1.09μg L-1) .There were no significant differences between vinasse and control (P<0.05).
3. Nitrate
The control group gave the highest average of nitrate (158.27 μg L-1) while the lowest concentration was recorded in vinasse treatment (25.78 μg L-1). There were significant differences between vinasse and control treatments (P>0.05). 4. pH
The highest negative logarithmic value of hydrogen ion concentration was recorded in control group (6.52) and the lowest value was concentration recorded in vinasse treatment (6.19). There were significantly differences between vinasse and control treatment (P<0.05).
5. Total suspended solids and volatile suspended solids
The highest values of total suspended solids and volatile suspended solids were recorded in vinasse treatment, while the lowest values were recorded in the control treatment. There were a significant differences between vinasse and control treatment (P>0.05).
6. Floc volume index and total bacterial count.
The highest floc volume index (FVI) and total heterotrophic bacteria (THB) were recorded in vinasse treatment and all readings about floc volume index and total bacterial count equal zero in the control treatment which was not treated with carbon.
7. Fish survival rate
The survival rates in the control and all treated groups were around 98 %. There were no significantly differences between all treatments (P>0.05).
8. Proximate composition of biofloc and fish The highest value of fish crude protein, ether extract and ash were recorded in vinasse treatment which were significantly higher (P<0.05) than that of the control treatments.
9. Body weights and growth performance
Vinasse treatment yielded the highest values of growth parameters (TWG, SGR, Net yield, Final body weight) and best nutritional parameters (FCR, PER and NPUa). While the lowest values were detected in control group. The statistical analysis showed that there were no significant differences in growth and nutritional parameters among vinasse and control group (P<0.05).