The nitrogen pollution of freshwater heavily affects social-ecological systems. To reduce negative effects, research calls for an integrated approach, including a coherent and diverse set of governance instruments. Thus far, however, the effects of (non-)integration have been blurry. Taking Germany as an example, this study sheds light on the actual complexity of the problem along five dimensions of complexity (goals, variables, dynamics, interconnections, and uncertainties). It also sheds light on related governance instruments (rules, information, and economic incentives) and their impacts on problem-solving (implementation of specific measures). Analyses include expert interviews on complexity, European water and agricultural policies, and official data on the planning and implementation of measures to reduce nitrogen concentrations. Results show Germany's path of sustaining a complex problem by using a non-coherent and low diversity governance approach, avoiding rigorous rules, and barely using economic instruments to deal with nitrogen surpluses. A stronger integration of water and agricultural policies, as well as a better use of economic instruments, are suggested to enhance water quality in the future.