What is a betta fish? Betta fish—also known as Siamese ... and are a dull gray, green, olive, or brown. Before mating, the male spends hours blowing bubbles at the water’s surface to build ...

These colorful patches appear with shimmering, iridescent scales. More expensive koi betta fish might have splashes of blue, green, pink, or purple. Koi betta fish tend to be aggressive and unfriendly ...

Betta, or Siamese fighting, fish are among "the most popular freshwater aquarium fish in the world," PetMD reports. Native to southeast Asia, this species is known for its range of vibrant hues.

For example, stress can temporarily make your betta fish look duller ... of special parts at the edges. This reef fish flips ...