The collection of the Botanical Museum of the University of Zürich is an academic collection assembled from 1891 to the end of the 20th century (1992 for the last inventoried item). Preserved plants come from all over the world (40 countries) and include all categories of existing Plantae (algae, lichens, fungi, higher plants, bacteriae). The fluid collection, largely neglected since 1976, shows significant degradation. The main problem is loss of preservative fluid due to leakage of the jars and aging of the seals. Another issue is the discoloration of the specimen fluids. These issues led to a research project titled FLUIDIS, which aimed to explore different preservative solutions and their impact on the discoloration of plant specimens. Conservation-restoration work was carried out on the jars of the “Professor Ernst Collection.” Topping up of was necessary for the entire collection. Restoration was performed after opening the containers and identifying the fluid. The specimens were consolidated, repaired, and mounted when necessary, then gradually put back into alcoholic solutions and finally sealed. An overall intervention protocol was established for the treatment of the entire botanical fluid collection. Its application, however, requires a careful study of each specimen.