Abstract: To determine the optimum proportion(R/ H ratio)of two bacterial strains, the Rhodovulum sulfidophilum and the Halomonas alimentaria were immobilized with sodium alginate and added to purifying bio-ceramic units in different proportions. The purification effects was tested in the recirculation aquaculture seawater system by observing the removal rate of nitrate, nitrite and ammonia as the purification index. The results showed that a highest removal rate of nitrate and ammonia at a R/ H ratio of 75%, even in the water conditions with lower ammonia concentration. At the R/ H ratio, the removal rates of ammonia, nitrate and nitrite were 79.72%, 90.61% and 77.06%, respectively.

Key words: Denitrifying bacteria, Photosynthetic bacteria, Aquaculture water, Purification effect