Airtech Air Pumps are excellent quality and provide high performance for all fishkeepers. The diaphragm pump is well engineered, robust and durable. This complete kit contains everything you need to create a smooth connection and a vibrant stream of bubbles in your pond from the pump to air stones. The air pump can handle around 70 litres per hour so it\'s great for a pond with a volume 500 litres (370 if keeping fish and 170 if keeping koi). As the kit includes 2 air stones you can create a steady stream of bubbles to distribute oxygen around the pond and keep the water as fresh and healthy as possible. Using an air pump and stone will create movement within the pond which shares the oxygen in the water around more evenly. This creates a healthier environment and avoids any stagnant patches which can cause poor water quality. This carefully constructed pump is reliable with low energy consumption making it cost effective all year round. As it comes complete with a two year guarantee, you can rely on Evolution Aqua.