Many fish prefer a finer substrate, such as sand. Bottom dwellers like corydoras and kuhli loaches like to sift the sand through their gills, looking for tiny food particles, so the finer the sand, the better. Some bottom dwellers need a fine sand because a course gravel will cut and irritate their underside. Some fish even burrow, and need a fine sand to protect their skin from cuts. But are there any fish that prefer course gravel? I know course gravel is easier for plants to root in. But what about fish? Are there any fish that would rather have rough gravel?