Was skiing a few weeks ago in Japan and i saw this system under one of the gondola's.

Uses flow from snow melt off (the whole village is a mad contraption of pipes, open gutters and rushing streams. Legal nightmare. You are surrounded by flowing water on all sides due to the snow run-off). Had hundreds of fish in each of the 3 levels. I dont know what they where, but you can just see some of the blond/gold looking ones in the top tank in one of the shots. Hundreds more dark grey ones that the camera didn't pick up. Possibly trout as we ate some very small trout in a few of our meals...

I thought people may be interested....