All fish species both freshwater and saltwater, have similar behaviors. Some of these behaviors may be odd in some species while normal in some. For instance, sitting at the bottom of the tank may be abnormal behavior for some fish species but it's normal for catfish.  Other fish behaviors include: *Hiding.  *Fighting. *Erratic Swimming *Listlessness. *Sitting on the Bottom of the tank. *Gasping for Air. *Reproductive Behavior. *Ambisexual Fishes Reproductive Behavior.