The observed THB levels found during the first phase was slightly higher than those found in other shrimp culture ponds (Devaraja et al., 2002 and Tendencia et al., 2006). Devaraja et al. (2002) reported that the THB levels were 3.75 × 105 CFU/g in pond bottom soil collected from black tiger shrimp ponds. Tendencia et al. (2006) reported levels of THB in shrimp pond bottom soil, ranging from 5.4 × 105 CFU/g to 6.8 × 105 CFU/g. However, in tilapia pond bottom soil the number of THB was much higher, ranging from 1.2 ± 3.1 × 106 CFU/g to 7.3 ± 1.1 × 107 CFU/g (Al-Harbi and Uddin, 2005). Low values of THB of under 0.58 ± 0.07 × 106 CFU/g at the end of experiment in the third phase indicated that drying of soil in sunlight reduced the number of heterotrophic bacteria.