With no doubt the winter has bright sides. However for a Koi the winter means stagnation of growth and in spring, when the water is getting warmer there is the risk of dying by a thermal shock. However there are possibilities not to cool down the pond too strong
Pond covering, consisting of balls filled with argon. Just pour on the water until the pond surface is covered. Argon is a noble gas, which has
a very poor thermal conductivity. Areas that you want to keep free (for feeding) have to be kept free hose assembled to a circle.
Furthermore, we can offer you a heat pump (air system) to keep your pond warm. The heat pump has an incredible efficiency of 1:8. This means that with every kilowatt of electricity the pump produces 8 kilowatts of heat output for your pond. We use Argon-balls and heat pumps ourselves.