What a beautiful pond...! Quite surprised to see a thread like this here, though related. My wife and I constructed three ponds and two have Koi while the one has very large and fancy Goldfish. As far as the green house goes...Great idea and I am sure if your partner is as handy with tools as he/she is, it will turn out just as nice as your pond. We built thatch type roofs over ours for the sake of keeping the sun from steaming the fish. It also protects the fish from all the unwanted 'stuff' that is in the air. We happen to live in a beautiful part of the world where it is 85* on average. Chiang Rai, Thailand.