To maintain a healthy fish population in a pond, it is important to manage the pond's environment carefully. This involves monitoring water quality, feeding fish appropriately, and avoiding overstocking with fish. It is also important to provide adequate habitat and shelter for fish in the pond. Additionally, practicing catch-and-release fishing can help maintain a healthy fish population by allowing fish to spawn and reproduce. Proper management of a pond's ecosystem will ensure a sustainable and healthy fish population for years to come.