The increasing demand for protein from aquaculture will trigger a global expansion of the sector in coastal and offshore waters. While contributing to food security, potential conflicts with other traditional activities such as fisheries or tourism are inevitable, thus calling for decision-support tools to assess aquaculture planning scenarios in a multi-use context. Here we introduce the AquaSpace tool, one of the first Geographic Information System (GIS)-based planning tools empowering an integrated assessment and mapping of 30 indicators reflecting economic, environmental, inter-sectorial and socio-cultural risks and opportunities for proposed aquaculture systems in a marine environment. A bottom-up process consulting more than 350 stakeholders from 10 countries across southern and northern Europe enabled the direct consideration of stakeholder needs when developing the GIS AddIn. The AquaSpace tool is an open source product and builds in the prospective use of open source datasets at a European scale, hence aiming to improve reproducibility and collaboration in aquaculture science and research. Tool outputs comprise detailed reports and graphics allowing key stakeholders such as planners or licensing authorities to evaluate and communicate alternative planning scenarios and to take more informed decisions. With the help of the German North Sea case study we demonstrate here the tool application at multiple spatial scales with different aquaculture systems and under a range of space-related development constraints. The computation of these aquaculture planning scenarios and the assessment of their trade-offs showed that it is entirely possible to identify aquaculture sites, that correspondent to multifarious potential challenges, for instance by a low conflict potential, a low risk of disease spread, a comparable high economic profit and a low impact on touristic attractions. We believe that a transparent visualisation of risks and opportunities of aquaculture planning scenarios helps an effective Marine Spatial Planning (MSP) process, supports the licensing process and simplifies investments.