Betta fish sleep at night or when it is dark. Since they do not have eyelids, betta fish sleep with their eyes open. They often look pale when they sleep.
Betta fish usually take shelter beneath plant leaves when they sleep, but sometimes they float on the surface of the water or hover motionless in the water. They assume an L-shaped posture when they sleep. Betta fish require a dark environment for sleeping. It is recommended that aquarium owners turn off the lights at night to allow pet betta fish to sleep. Keeping the aquarium illuminated around the clock may have a negative impact on the betta fish's health.