Fish are highly decorative beasties, especially koi. Unfortunately, they live down in ponds where they are hard to see well enough to paint. Here is a fun solution to the problem of getting a good look at koi from the side.
(The video also helps to answer the question of whether fish are unhappy in a tank. I have always suspected that my goldfish are. They seem rather like cows. They spend all day grazing – busily picking through the gravel and munching on the plants. They recognize different people and hide from scary strangers. They beg for algae wafer treats when they see someone they recognize. They snuggle up with each other to sleep. Maybe my goldfish would not have chosen to be born feeder fish in an aquarium, but they seem content living with me, even though I don’t have a large pond for them. And this video makes me wonder if they might not perhaps like the view from tank better.)