Many aquarists keep brightly colored tropical species. There’s nothing wrong with that, but keeping native fishes in a glass box can provide you with better insights into the behaviors of their wild brethren. Sometimes this is impractical — keeping a tarpon requires a Bass Pro Shops-size tank, which you probably don’t have room for and your wife won’t let you build it anyway. (If she will, let me know — I’m coming over to take pictures.) Most saltwater gamefish are too large to keep in a home aquarium, at least when they’re legal size.