The most likely determinants of the distribution of Sicyases sanguineus are areas where vertical rocky shorelines encounter ocean swells and ample benthic prey.

[2] Sicyases sanguineus attaches by means of a large disc formed of the fused and highly modified pelvic fins, bearing small and flattened dermal papillae.

[2] Sicyases sanguineus is omnivorous, feeding on a wide range of algae (brown, green and red) and many types of invertebrates (especially molluscs such as chitons, marine snails, limpets and mussels, and barnacles, but also crabs, isopods, amphipods, insect larvae and sea urchins).

For example, they have been observed living in apparent peace with large chitons and limpets, whereas the small individuals are eaten by this clingfish.

[6] A second mode in which Sicyases sanguineus feed on them is to insert its teeth on the limpet's shell and then twist.