All of these fish may display territorial and/or aggressive behavior to members of the same or similar species. For example, a flying fox may harass a SAE. SAE's are said to tolerate others of their own species (but not related species), at least while young. These fish all swim around virtually non-stop. This is due to an underdeveloped swim bladder. When there is more than one, they will chase each other and wear each other out.