Under an ecological speciation scenario, the radiation of African weakly electric fish (genus Campylomormyrus) is caused by an adaptation to different food sources, associated with diversification of the electric organ discharge (EOD). This study experimentally investigates a phenotype-environment correlation to further support this scenario. Our behavioural experiments showed that three sympatric Campylomormyrus species with significantly divergent snout morphology differentially react to variation in substrate structure. While the short snout species (C. tamandua) exhibits preference to sandy substrate, the long snout species (C. rhynchophorus) significantly prefers a stone substrate for feeding. A third species with intermediate snout size (C. compressirostris) does not exhibit any substrate preference. This preference is matched with the observation that long-snouted specimens probe deeper into the stone substrate, presumably enabling them to reach prey more distant to the substrate surface. These findings suggest that the diverse feeding apparatus in the genus Campylomormyrus may have evolved in adaptation to specific microhabitats, i.e., substrate structures where these fish forage. Whether the parallel divergence in EOD is functionally related to this adaptation or solely serves as a prezygotic isolation mechanism remains to be elucidated. by Tonio Pieterek. Matlab scripts were inspired by Volker Hofmann.Author's contribution RA participated in the design of the study, carried out the experiments, analysed the data and drafted the manuscript; RN participated in the design of the experiment and critically revised the manuscript; MH carried out the feeding experiments of the C. tamandua individuals under the supervision of RA and RT. RT and FK conceived, participated in the design and coordinated the study. RA and RT revised the manuscript after an initial review. All authors have read and approved the manuscript for publication.