What is a common behavior of fish when they are stressed?

When fish experience stress, one of the most common behaviors they exhibit is hiding or becoming inactive. This response is an instinctual survival mechanism. In the wild, when fish are faced with threats or stressors, such as changes in water quality, the presence of predators, or social stress, they often seek refuge in structures or vegetation where they feel safer. This behavior helps them avoid potential dangers and conserve energy.

When fish become inactive, it can be a sign that they are trying to cope with their environment. Increased hiding also reflects a desire to escape from stressors, revealing their instinct to protect themselves. In contrast, behaviors such as increased curiosity, aggressive feeding, or aggressive schooling might not align with stress responses, as these behaviors typically indicate comfort or a lack of threats, rather than the presence of stress. Thus, the choice of hiding or becoming inactive is a clear indicator of stress in fish.