You can use a mix of filtration methods to efficiently filter a 500-gallon pond that is heavily stocked. A biological pond filter should be considered first. To further ensure the pond remains clean and avoid biological filter overload, it is essential to use a mechanical filter to physically remove organic waste, debris, and dirt from the water. It is crucial to include aeration into the pond to guarantee enough oxygenation and avoid stagnation. Your heavily stocked 500-gallon pond can be successfully filtered and kept fish-friendly by following these instructions and taking your pond's unique requirements into account.