I started wondering how it is that fish don't crash into the side of the tank. After all, they have no binocular vision, and their brain can't possibly be big enough to learn about things like invisible barriers.
The fish aren't using their eyes to "see" the glass, but rather a special pressure-sensing system called the lateral line. This system is made up of sensory units called neuromasts, consisting of cells on the body surface that have a projecting hair encased in a gelatinous cap. When pressure waves in the water move the gelatinous caps and bend the hairs, the firing rate of nerve impulses sent to the brain by the neuromasts changes, enabling the fish to detect the waves.
Fish set up pressure waves as they move through the water, and are able to detect the reflection and distortion of these waves from objects and thereby avoid them. They are also able to detect the pressure waves of other fish.
That's really awesome. Who'd have thought that a silly comic would lead to learning such interesting trivia. Go read the rest of the article for more interesting related facts.