Many people assume that goldfish cannot make nests, but this is not necessarily true. Goldfish are actually capable of making nests when the conditions are just right! The first step involves finding a spot in the aquarium with plenty of plants and gravel for cover. This is where they will build their nest. Once they have chosen an area, they begin to fan out the debris with their fins until it forms a mound or hill-like shape on the bottom of the tank. The next step involves collecting pieces of vegetation such as algae, weeds, and bits of leaves and placing them around the edges to help hold up the structure. Finally, some species may add other materials like small stones or shells to give their nest additional support and camouflage. No matter what species you have in your tank though, providing an adequate food supply can help encourage these fish to create a nesting site since they need energy to do so!