Yes, koi do need a filter system to thrive in a pond environment. Koi produce a large amount of waste, which breaks down into harmful substances like ammonia and nitrites. Without proper filtration, these toxins can quickly build up and lead to poor water quality, stressing the fish and increasing the risk of disease.
A good filter system not only removes physical debris but also supports beneficial bacteria that help break down waste through biological filtration. This creates a stable, healthy ecosystem that mimics the natural processes found in lakes and rivers. Even if the water looks clear, harmful compounds can still be present, so a filter helps maintain long-term koi health and pond clarity.
