Hydrogen sulfide is toxic gas produced by microbes. Controlling H2S production is important for the aquaculture industry, since H2S is extremely toxic for the fish, causing production losses and hindering the growth of aquaculture sector. In this REACT2S-project, I will gather new scientific knowledge on the identity and function of H2S producing microbes and on the biochemical pathways they use for H2S production. I will apply this knowledge to suggest alternative bioreactor design and operational parameters for aquaculture industry to control H2S production.