4. Fish

There are some 25,000 species of fish that have been discovered so far and fishing is the second most popular hobby of people in America. Keeping a fish has always been a favorite of people looking for pets because it brings both company and relaxation. There is a good amount of serenity exuded by the still water in which the fish calmly swims. It brings relaxation and soothes the mind. Watching slow moving fish swimming in the aquarium is relaxing for people with hyperactive minds.