S. guntheriforage mostly during the day, though some night activity has also been recorded. These fish graze on microscopicalgae, mostly diatoms and green algaegrowing on rocks and submerged vegetation. They occasionally take chironomid and simuliidlarvae. Before grazing on a patch with dense sediment, a fish makes wiggling head-down movements to dislodge sediment. When scraping algae off the substrate, it makes vigorous mouth movements, and moves by jerky movements probably related to its mouth alternating between grazing and attaching to the substrate. Grazing leaves characteristic, parallel and elongated marks on the substrate.