Hatchet fish are a rare kind of fish that stay at the top of the tank. Most fish dwell either at the bottom or the middle.Hatchets however are nearly always right at the surface of the tank. Having these fish in your tank makes it look a lot more full. They are community safe fish that are peaceful. Most hatchets aren't the fastest swimmers and have long tails, so they shouldn't be kept with fish that harass other fish.