As the last application of our microfluidic device, we decided to size-sort, and detect plankton from water. Monitoring plankton, especially zooplankton, is one of the best indirect methods to check the ecological health of water bodies. Climate change and pollution modify the zooplankton population, which can be monitored over a long period by comparing the population distributions over time. Also in this case, collecting the sample using nets, or filtering large amounts of water before bringing the sample back to the lab, is lengthy and laborious, not really in line with fast and straightforward on-site, possibly citizen-science driven, plankton detection.