Fish staying still can be an indication of several things. It could mean that the fish is resting or conserving energy. Some fish species have the ability to remain motionless for extended periods to camouflage themselves from predators or prey. Alternatively, fish may stay still when they are feeling stressed or fearful. In an aquarium setting, fish may freeze in place due to changes in water temperature, poor water quality, or high levels of noise or disturbance. It is important to monitor their behavior and the surrounding conditions to ensure their well-being.