At the back of the Manulife Centre, a luxury shopping mall along the “Mink Mile” in downtown Toronto, in an unassuming corridor of the movie theatre, is a piece of décor that is totally unremarkable for any corporate lobby, yet surprising when given a moment of pause: a saltwater fish tank, featuring a live coral reef. The fact that this and other publicly displayed aquaria have not yet been replaced with flat screens playing a 10-hour YouTube video on loop, “Best 4K Aquarium for Relaxation and Calm Sleep Music UHD,” stands out among today’s ornamental impulses, especially because of the murky challenge of keeping an aquarium’s micro-cosmos in delicate equilibrium (I say so, sadly, from experience). Aquarium fish remain ubiquitous in day-to-day life and are found in settings ranging from restaurant interiors, to tourist attractions, and medical waiting rooms. By sheer numbers, they are among the world’s most popular pets and comprise a multibillion-dollar industry, per a study of the global pet fish trade.