Seaweed has the potential to deliver more food to an increasing world population. Diseases endanger production security and yield of any farm, seaweed farming is no exception, hence crop protection plans may be developed that include the use of chemical crop protection either directly or indirectly in co-cropping systems. This document reports a first attempt to map the extent to which chemicals are being used in seaweed production, which production systems are used, where potential risks of the use of chemicals resulting from protection of seaweed production (or co-produced products) against diseases can be anticipated, and how this could be taken into account for future work. The investigations concerning open sea production systems indicate that for the control of pests and diseases in the described cultivation systems only prevention, monitoring and mechanical/physical measures are common, at least for Indonesia. In contrast, results from closed pond- or tank-based multi-trophic systems where seaweed can be included for example as feed or filter, or for biomass production, indicate some reasons for concern. Uptake and sorption of veterinary medicinal products and other chemicals can lead to additional input to shrimp and/or fish (via feed) or to the environment (via disposal of filter material). The ERA-AQUA model, originally developed for risk assessment of aquaculture production of fish and shrimp, was identified as possible means to further explore the fate of chemicals used in land-based multi-trophic production systems, for their bioaccumulation and biomagnification potential and possible risk for the environment, the produced goods (fish/shrimp), and finally human health.