ADDITION OF PHOSPHATE OR NITRATE BEFORE STOCKING INCREASE SURVIVAL RATE IN BLACK TIGER SHRIMP PENAEUS MONODON NURSERY

Nitrogen and phosphorus are two macro mineral that highly determine shrimp pond productivity. Moreover, pond water quality closely correlate to types, concentration and ratio of nitrogen and phosphorus. This study aimed to identify the dynamics of biological and chemical water quality variables when treated by ammonium sulfat (ZA), potasium nitrate (KNO₃), and sodium dihidrogen phosphate (NaH₂PO₄)  and its correlation to survival rate and growth in 21 days of culture. To anticipate high variation of nitrogenic substances, more replication was provided. Nitrogen test consisted of 4 treatment and 5 replication i.e. control, 2,5 ppm KNO₃, 2,5 ppm ZA, 2,5 ppm KNO₃ + 2,5 ppm ZA.  Phosphate test consisted of 4 treatment and 3 replication, i.e. 0 ppm NaH₂PO₄, 1 ppm NaH₂PO₄, 5 ppm NaH₂PO₄, 10 ppm NaH₂PO₄.  After treatment, seawater (32 ppt) was let down for a week. Shrimp post larva stocked with density 50 ind/25 l, feeding frequency 3 times/day and feeding rate 1,5 ppm.

The result revealed that survival rate of KNO₃ and KNO₃+ZA (SR 75% dan SR 73%) were better than control and ZA (SR 68% dan SR 58%) (Figure 1). One and 5 ppm NaH₂PO₄ achieved better survival rate (SR 90% dan SR 94%) than 0 dan 10 ppm (86% and 76%) and also the length (Figure 2). Total bacteria increase sharply for control and ZA (80 and 100 times) that was higher than KNO₃ and KNO₃ + ZA (40 and 45 times). Total vibrio increased sharply in the first week after stock, i.e. 44 times (control), 72 times (KNO₃), 107 times (ZA) and 155 times (KNO₃ + ZA). Total vibrio developed constantly when NaH₂PO₄ concentration increased. Control and ZA revealed more species of phytoplankton i.e. 25 and 21 species but KNO₃ and ZA only 15 and 12 species. Sixteen species of phytoplankton was found in 0 ppm NaH₂PO₄ and decreased become 8-10 species when concentration of NaH₂PO₄ increased to 1-10 ppm. One ppm and 5 ppm NaH₂PO₄  revealed 75% of the same phytoplankton. Survival rate likely correlated with total bacteria and phytoplankton species. It could be concluded that 2,5 ppm KNO₃ and 1-5 ppm NaH₂PO₄ showed better shrimp and water quality performance than the other treatment.