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3rd Experiment






N S   S E R I E S

 Mega SPO   


Thiobacillus denitrificans


Paraccocus denitrificans


High Density

Prawn & Fish Culture





2 Growth Stages     


Third Experiment

Effects of SPO in two growth stages of prawn (61, 100 day-old P.monodon)

Determination of the optimum dosage application of NS Series SPO




Eighty pieces each. of prawns belonging to two (2) stages of growth A = Stage I (61 day-old), B = Stage II (100 day-old),  obtained from Nasugbu, Batangas were transported to the experimental site. Upon arrival, the transported prawns were placed in 100-liter capacity tanks containing 40 liters of pond water with a salinity of 26 ppt.  The set up was provided with moderate aeration. The experimental animals were conditioned to its new environment for 24 hours. They were then acclimated to a water salinity of 18 ppt prior to the conduct of the experiment.

Eight pieces each of prawns representing the two stages of growth indicated above were stocked in 18 units of 100-liter capacity tanks containing 30 liters of water at 18 ppt or an effective stocking density of 33.6/sq.m.
  Three dosage levels of NS Series SPO were inoculated to each tank as follows:

g/cu.m.   g/30 Ii
I 0.5 0.015
II 1.0 0.030
III 1.5 0.045



The required amount of NS Series SPO was applied by preparing a stock solution of 1 gram of culture in 1 liter of water.  Aliquot amounts were added in each tank i.e. 15 ml, 30 ml, and 45 ml each for treatments I, II and III respectively. Prawns were fed with commercially prepared diet (SMI-President Feeds) used in earlier experiments given at 12% BW. Feed ration for the day was divided into six equal parts and fed to the prawns at every 4 hours interval.

The physio-chemical parameters of the rearing water were closely monitored as in the first two experiments. These consisted of pH, D.O., nitrite, ammonia and total solids (unconsumed feeds and fecal matter). Samples were taken initially and every two days thereafter using standard methods.
  No water change was done for the entire duration of the experiment which lasted for 14 days.  Initial and final length and weight of the test animals were taken. The survival of the test animals in each of the treatments were taken at the termination of the experiment.




Effect on the Nitrite level


Varying dosages of NS Series SPO (0.5, 1.0, 1.5 g/cu.m.) inoculated into the growing medium of prawns did not produce differences in the nitrite level. In all the treatments, the values were maintained well within optimum limits which were set at 0.1 ppm - 0.5 ppm for nitrite.

Among the three inoculum levels applied, no marked differences in the nitrite levels were observed during the conduct of the experiment which lasted up to 14 days. This means that 0.5 g/cu.m. which is the lowest rate of application of NS Series SPO is sufficient to reduce the nitrite content of the water to a safe level. This may be explained by the fact that bacteria multiply and grow as long as there is available substrate in the environment.

In both the 61 day-old prawns and 100 day-old prawns, the three dosages of NS Series SPO were equally effective in controlling the nitrite levels within optimum limits. This demonstrates the efficiency of the bacteria inoculated in the growing medium which act on higher amounts of uneaten feeds and fecal- matter as the prawns grew older.  Statistical analysis showed no significant: differences among the three dosages of NS Series SPO for two growth stages of prawns. 



Effect on the Ammonia level 


The ammonia level in all the treatments remained very low and within tolerable limits set for prawn. The same trend was observed, that is, there were no differences in the ammonia level of the water inoculated with varying dosages of bacteria. The rearing water in both Stage I (61 day-old) and Stage II (100 day-old) prawns showed comparable values throughout the experimental period.




Effect on Dissolved Oxygen

The varying levels of bacterial inoculation produced comparable values of dissolved oxygen. The D.O. levels in levels in the various treatments were all greater than 3.5 ppm, the optimum limit set for prawn farming.


Based on the above results, bacterial inoculation may be reduced to 0.5 g/cu.m. without adversely affecting the D.O. level in the water. Moreover, bioaugmentation of NS Series SPO at the start of the culture period prevented the accumulation of organic matter in the medium. This being the case, there were no drastic reduction in the D.O. level since decomposition occurred gradually with time. 



Total Solids

The total solids content of the rearing water inoculated with three levels of bacteria were comparable for specific stages of growth of prawns. Note that the total solids content of the 100 day-old prawn ii is 2 to 3 times more than in the younger (61 day-old) prawn. This demonstrates further the efficiency of NS Series SPO given at a low dosage of 0.5 g/cu.m.


The bacterial population did not differ among the different levels of inoculation. Since bacterial growth is dependent on the amount of substrate in the medium, the amount of substrate (waste materials) available can only support bacterial growth to this level.  Between the two growth stages of the prawns, similar bacterial counts were also observed. Apparently, the minimum amount of bacteria applied (0.5 g/cu.m.) has the capacity to efficiently decompose even the higher substrate level produced by Stage II (100 day-old) prawns. Statistical analysis did not show significant differences among the various treatment dosages.


Statistical analysis showed no significant differences among the three dosages of NS Series SPO inoculated in the rearing medium for both 61 day-old and 100 day-old prawns.

Effect on Prawn Growth and Survival
High survival of prawn (2 growth stages) in a closed semi-controlled culture system without water change was observed in all the treatments. Survival values ranged from 87.5% to 95.8%. This may be attributed to the maintenance of good water quality throughout the duration of the experiment.

Duncan's Multiple Range Test did not show significant differences among the three varied dosage applications.







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