The increasing demand for high-quality protein supplied through aquatic animal products causes aquaculture to be the fastest growing food production sector in the world. A further sustainable expansion of the sector is hampered by the frequent outbreak of bacterial diseases. The current solutions include the use of antibiotics, which is unsustainable due to the development and spread of antibiotic resistance, and the use of biological control measures (e.g. probiotics), which currently provide insufficient protection. This urges the need for development of effective, sustainable management strategies. An integrated approach where the microbial community is monitored and manipulated has been suggested as a promising solution. Although some studies have addressed this issue, in depth knowledge on how the microbial community is influencing the invasion potential of opportunistic bacterial pathogens and in which way the community should be steered to avoid invasion are lacking. By means of this project we want to gain insight regarding the invasion susceptibility of aquaculture systems. We will focus on the diversity of the community, while taking into account the typical environmental conditions of aquaculture systems and the opportunities that this provides to opportunistic pathogens. We aim to reveal which community properties are to be targeted to steer the microbial community, and in this way we will provide a framework for development of novel management strategies.