Fish can live in a natural swimming pond, but their presence requires careful balance to maintain water quality. They produce waste that adds nutrients to the water, which can lead to algae growth if not managed properly. A well-designed ecosystem with sufficient aquatic plants and beneficial bacteria helps break down waste and keep the water clear.
Certain fish, such as koi and goldfish, may disturb plant roots, while others, like mosquito fish, help control insect populations. Providing enough space and maintaining proper oxygen levels ensures a healthy environment for both swimmers and aquatic life. Regular monitoring of nutrient levels and occasional maintenance, such as removing excess organic matter, helps prevent imbalances.