In the RAINBOflow Chip project, we are developing a biosensor system to detect toxic effects of chemicals by impedance sensing. At the core of the biosensor are cell lines from the rainbow trout (Oncorhynchus mykiss), which can predict toxic effects to fish. They are seeded on a microfluidic chip where their adherence to the electrodes creates a resistance to an applied electric current flow. This resistance reflects the health status of the cells; a decrease in resistance is an indicator for loss of cell viability. This method is quick, non-invasive, and can be automated, thus it allows monitoring toxicity in real-time. Our aim is to employ this method for time-resolved toxicity testing of chemicals under flow conditions, as well as to establish a portable and compact system for use in the field, with the data being accessible online to inform about the current water quality.