Pheromones are chemicals that carry messages that produce behavioral responses in other fish. Different species of fish uses different chemicals, which usually makes it hard for different species to communicate with each other. Pheromones can communicate a number of messages ranging from whether or not danger is looming, food is present, or mating is to occur. The reactions to pheromones are automatic and observable under certain circumstances. Social pheromones exist as well, cueing fish in on whether or not they are too crowded together or lonely etc.
Fish can also change their color as an indicator of their mood.
The way a fish changes depends on their species. They also use these color changes to aid mating and fighting rituals. Some can even control pigments that produce stripes on their bodies, which confuse predators chasing them. In general fish have very intricate and interesting communication techniques, make sure to try and observe any pets you have to see if you can detect these changes. Inc. Pagewise makes no representations about the content published on this site.