EcoToxFred is a prototype that demonstrates how domain-specific knowledge can be combined with LLMs to facilitate the interaction between users and (domain-specific) knowledge. EcoToxFred can answer questions about chemicals and their measured concentrations in European surface waters like rivers and lakes. EcoToxFred is a friendly and intuitive chatbot designed to help researchers, stakeholders, and users explore and analyze chemical concentrations and toxicity data in European surface waters. By leveraging advanced language models and a graph database, EcoToxFred makes complex environmental toxicology data accessible and understandable for everyone, regardless of their technical background. The web application is accessible at https://ecotoxfred.web.app.ufz.de/.