Why is my fish losing colour?

Why this happens

Fish colour is produced by pigment cells and reflective structures influenced by hormones, background, mood, breeding condition, light and health. Some species deliberately fade at night or under submission.

• Transport and netting can cause temporary paling.
• Dominant and subordinate fish may display different colour.
• Poor diet can reduce pigment condition over time.
• Anaemia, parasites or systemic disease may cause persistent pallor.

Compare photos taken under the same light. Camera white balance and aquarium LEDs can make colour changes appear larger than they are.

What to check first

• Is the change sudden, patchy or whole-body?
• Does colour return at feeding or after lights-on?
• Are appetite, breathing and body condition normal?
• Is the fish being chased or excluded?

Compare the result with the aquarium’s normal baseline, not only a generic target. Record the time, recent maintenance, new livestock, feeding changes, source-water details and any equipment fault. A short timeline often separates the original cause from secondary symptoms.

A practical action plan

1. 1. Stabilise the environmentConfirm water quality and remove obvious social stress.
2. 2. Review nutritionProvide a species-appropriate varied diet without overfeeding pigment products.
3. 3. Document the patternPhotograph daily under consistent light and note behaviour.
4. 4. Escalate if signs accumulateQuarantine or seek veterinary assessment if pallor accompanies weakness, sores or rapid breathing.

How to interpret the response

Colour that returns after acclimation or reduced aggression supports a stress response. Progressive fading with weight loss or respiratory signs is more concerning than a stable change alone.

Change one important variable at a time where welfare allows, then observe and retest. When several products or adjustments are made together, it becomes difficult to know what helped, what caused stress and whether the underlying problem remains.

What to avoid

Do not use colour-enhancing food as a substitute for diagnosis, change lighting abruptly, or treat parasites solely because the fish looks pale.

When it is urgent

Very pale gills, collapse, bleeding, rapid breathing, severe weight loss or several fish fading after a water change requires urgent investigation.

How to prevent it next time

Provide species-appropriate social groups, stable lighting, quarantine and balanced food while keeping comparison photos.

Keep enough records to recognise the aquarium’s normal behaviour, water chemistry and equipment performance. Trends are more useful than isolated numbers, and early correction is usually safer than a large emergency change.