Scientific literacy is becoming increasingly important for teachers in the current knowledge landscape, where fake information is gaining ground. However, little is known about how fake content becomes part of ordinary knowledge in science education. This study investigated how Finnish student teachers recognised fake content on the topic of biodiversity loss in an online learning environment and how they used it. Seventy-one first-semester primary student teachers at a Finnish university were given the task of writing a synthesis using online sources and evaluating those sources. The learning environment included relevant, irrelevant and fake texts. The analysis used quantification, content analysis and discourse analysis. The findings showed that nearly half of the participants used fake content in their synthesis, while they also succeeded in synthesising relevant texts. We focused on the use of fake content and identified three discourses referring to it: (1) fake as fact, (2) fake as second opinion and (3) fake as suspicious. The study's implications regard improving curriculum development and programme design in teacher education.