It's true, that's why i'm considering to convert it in"indoor pond", my wife is close to agree !! she became to ask me to see the different Big Cichlid !!It's easily big enough, but I doubt you can heat it warm enough, even in south france. 35k litres (9500 Gallons) is a lot of water.
If i could close the pond, it would not be a problem to warm all the water for me.