1000 Euro-matic 50mm Natural Koi Carp Pond Swimming Pool Insulation Cover Balls

For fish such as Koi Karp, a cover in the winter months will help retain the heat and ensure they remain active rather than dormant. Because the balls simply move, the fish can easily be fed or viewed and fish that remain above 10°C will be active all year round so continue to grow and remain healthy, below 4°C it can be fatal.