In the present study, the results showed that B. subtilis
BS7.29 could reduce the NH3-N, NO2-N concentrations in
aquaculture water. The most significant effect appeared
when the cell concentration was 107 cfu/L. After treated by
this strain for 20 days, NH3-N degradation rate was 97% and
NO2-N degradation rate was 60%. This result was consistent
with the reported optimized concentration: 104 cfu/mL (107
cfu/L) [15]. It had also be reported that the NH3-N
degradation rate of another B. subtilis strain was 59.61%,
while the NO2-N degradation rate was 86.7% [16], indicating
that different B. subtilis strain might show different
degradation ability for NH3-N and NO2-N. To our opinion,
the compound use of different strains might be considered in
the future application.