Three hundred milliliter of M. aeruginosa in three different initial densities (low-, intermediate-, and high-density: 103, 105, and
107 cells/mL, respectively) was added into three separate 500 mL Erlenmeyer flasks with sterile silica gel-stoppered. N. minor (5 g- living weight) was added and co-cultured with the M. aeruginosa. For control, M. aeruginosa with the three densities mentioned earlier and N. minor (5 g living weight) were cultured individually. One mil- liliter concentrated stock solution (100×) of Hoagland medium was added to all the flaks each day to provide sufficient nutrient to the culture [5]. Triplicates of all the experiments were performed in an incubator with a light intensity of 120 μmol m−2 s−1 at 25 ± 1 °C and photoperiod 14L:10D for 12 days. M. aeruginosa density was moni- tored every other day. To evaluate reciprocal effect between M. aeruginosa and N. minor, at the end of the coexistence experi- ments, N. minor was separated from M. aeruginosa and cleaned with distilled water. The biomass of N. minor (living weight) was measured [5].