[Objective] Inorganic nitrogens (ammonium, nitrate and nitrite) existed simultaneously in complicated mariculture water. This work aims to explore the effects of organic carbons, especially seaweed oligosaccharides on the removal of inorganic nitrogens by a marine purple sulfur bacterium Marichramatium gracile YL28, which is capable of growth on nitrite as sole nitrogen source. [Methods] Sodium hypobromite oxidation, N-(1-naphthyl)-1,2-diaminoethane dihydrochloride spectrophotometry, and UV spectrophotometry were used for the determination of ammonia, nitrite and nitrate, respectively. Biomass was measured by turbidimetry. [Results] Under anaerobic light condition, organic acid salts (acetate, pyruvate, succinate, citrate) were better carbon sources for YL28, and the removal rate of ammonia, nitrate and nitrite reached 97.92%, 99.98%, and 73.23%?87.15%, respectively. Monosaccharides (glucose and fructose), disaccharides (sucrose and maltose) and oligosaccharides (chito-oligosaccharide and seaweed oligosaccharides) were also suitable for YL28 growth. The remove rate of nitrite and nitrate reached more than 99% and 87%, respectively. While the remove rate of ammonia was 44.82%?54.53%. YL28 had poor growth when polysaccharides (alginate, β-cyclodextrin, starch, xanthan gum, carrageenan and agar) as carbon sources. Yeast extract is favorable for YL28 growth, but it severely inhibited the removal of ammonia. Interestingly, the cell growth and inorganic nitrogen removal in combination of poor and good carbon source systems was equally well to that in good carbon source system. The combination of seaweed oligosaccharides and acetate sodium or yeast extract and acetate sodium promoted the increasing growth rate and biomass, however, there was a significantly different in removal rate of ammonium, seaweed oligosaccharides promoted the removal rate of ammonia, while yeast extract not. Under anaerobic dark condition, when using sodium acetate and ammonia as sole carbon or nitrogen source, YL28 grew poorly. However, under coexisting inorganic nitrogen environment, YL28 not only grew well but also removed efficiently inorganic nitrogen. [Conclusion] In coexisting inorganic nitrogen environment, whatever anaerobically in the light or dark, YL28 grows well and has better removal capacity to inorganic nitrogen. Organic acid salts are better carbon sources, sodium acetate is most suitable carbon source. The combination of seaweed oligosaccharides and sodium acetate could significantly promote cell growth and removal of inorganic nitrogen. This study provides valuable information for the development of higher efficiency water cleaner for sustainable mariculture.