I was skeptical at first because of the very reasonable price, but within 2 days after installation you could already notice a significant reduction in the amount of green in the pond water. Now after 5 days the water is almost clear. Super product with multiple connection options. Pond size 4500 liters with 3x / h pump capacity and a filter for a pond size up to 15 m³. Pay in 14 days irradiation at 12 h / day decrease