eReefs is a comprehensive information platform that simulates environmental conditions of the GBR region through coupled hydrodynamic, sediment and biogeochemical models. Nested within these models is the coral sub-model. The coral sub-model is unique as it operates from the perspective of the symbiont. It uses the build-up of reactive oxygen species (ROS), driven by temperature and light, as a bleaching proxy. We assessed its accuracy in predicting the onset and severity of bleaching using a tank experiment where corals were subjected up to 6.5 DHW with and without shade. The existing model parameterisation predicted 4 hours of midday shade to delay the onset of ROS expulsion by 2 days at 4 DHW. In an experiment using Duncanopsammia axifuga, a significant difference in the degree of bleaching, as indicated by mean intensity of grey was found between 4- and 12-hours shade at 4 DHW. This corroborates with the model prediction of a significant benefit from extra shade. The model currently has a single parameterisation for all corals, which this experiment has shown to be broadly applicable to D. axifuga. With additional species and physiological experiments, we aim to elucidate the accuracy of the model over a wide range of circumstances.