5 pet fish that change colour and why it happens

Many people who keep fish at home notice one common thing after some time. The fish does not look the same as it did earlier. The colour looks different. Sometimes it becomes brighter. Sometimes it looks dull. This change often worries new fish owners, but it is actually very normal.
Most fish change colour as they grow older. Some fish change colour because of their surroundings. Some react to stress, health, age, or environment. In nature, colour change helps fish stay safe and hide from danger. In home aquariums, the same process continues quietly.
For some fish, colour is also a way to communicate. For others, it simply shows how they are feeling. These changes happen slowly and naturally.
Here are five pet fish that are known to change colour and why it happens.
Disclaimer: The information in this article is intended for general awareness and hobbyist purposes. Fish colour changes can be influenced by multiple factors including species, genetics, diet, water quality, and health. The information is based on publicly available sources and general observations; it is not a substitute for professional advice.

Images: Canva (for representative purposes only)

Leaf scorpionfish can adjust their colour to blend into their surroundings. This ability helps them hide from predators and catch prey. It’s a natural survival mechanism, and their colours can shift gradually depending on their environment. (Note: leaf scorpionfish are specialist aquarium fish, not typical beginner pets.)

Peacock cichlids are known for their vibrant colours. Males often display their brightest hues during courtship or to establish dominance. Colours can also dull if they’re stressed or feeling subordinate. Changes reflect biology and social cues rather than “mood” in the human sense.

Goldfish are calm and beautiful fish. They are also known for helping keep freshwater tanks clean. Goldfish can change colour over time. This usually happens because of age, diet, and surroundings. They cannot change colour whenever they want. As they grow older, some goldfish may lose colour or change shade. Water quality and light also affect how their colour looks.

Betta fish are colourful and easy to care for. Many people choose them as beginner pets. Betta fish have unique fins and can change colour based on health, mood, and environment. Stress can make their colour look dull for some time. When they are kept in a clean tank and given proper food, their colour can return.

Koi fish are known for their calm movement and patterns. Their colour does not change suddenly. As koi fish grow older, their colours can become clearer and more defined. A balanced diet and clean freshwater help their natural colours look better over time.