Dealt with a few Koi ponds. Gonna need some good filtration...especially with those trees around it. A million gallons is quite an undertaking for a koi pond! How deep is it? What predators do you have around? Birds and mammals will destroy the koi as they like to be up at surface. Put some big hiding spots in for them to escape.
Thanx MaxH
The pond are 4 meter deep on its deepest. Birds are the biggest threat. It is normally no raptors in this part of Norway. But ... in a later video, you will see that they are here too ...
