How do you feel about Wabi Sabi? You know, that Zen Buddhist concept/aesthetic of accepting the impermanence and transience of all things. These nature aquariums by Japanese aquarist Takashi Amano are based on that idea. Think of bonsai, but underwater and with fish. That's what a nature aquarium is. His are quite beautiful, formal and ethereal, combining all the painstaking difficulties of miniature-making, regular plant gardening, zen rock gardening and aquarium maintenance. The plants are the focus in these tanks, rather than the fish. He has said that he starts with a piece of branchy driftwood, arranges it perfectly in the tank, and only then attaches the aquatic plants--ferns and willow moss, usually.
On a personal note, we keep an aquarium at my family's home. Each time we add new fish, it's survival of the fittest. We bought two miniature sharks, which were promptly eaten by the miniature barracuda. Events like these teach us how to accept the impermanence and transience of if not all, then some things.