Aquarium Fish Diseases: Symptoms, Causes & Treatment

Fish Diseases by Species

Each species Hub contains only links that appeared in the supplied Google Coverage export on 2026-08-24.

Common Aquarium Fish Disease Symptoms

Use the species Hubs to explore white spots, frayed or rotting fins, fuzzy growth, cloudy or swollen eyes, bloating, red streaks, rapid breathing, rubbing, appetite loss, floating, sinking and swimming sideways.

What to Check Before Treating a Sick Fish

1. Measure ammonia, nitrite, nitrate, pH and temperature.
2. Observe whether one fish or several fish show symptoms.
3. Check for recent additions or equipment changes.
4. Record symptoms and their progression; isolate a sick fish where appropriate.
5. Do not combine medications based on one visible sign alone.
6. Seek professional care for severe or deteriorating cases.

Sources and Editorial Method

Last reviewed: August 2026. Reviewed for: species naming, symptom terminology, water-quality guidance and source quality.

• Merck Veterinary Manual — Disorders and Diseases of Fish
• Merck Veterinary Manual — Management of Aquarium Fish
• World Organisation for Animal Health — Aquatic Animals

Frequently asked questions

What are common aquarium fish disease symptoms?

Common warning signs include spots, fin damage, swelling, unusual swimming, appetite changes, rapid breathing and changes in colour or waste. Similar symptoms can have different causes.

Can poor water quality make fish look sick?

Yes. Ammonia, nitrite, unsuitable temperature, unstable pH and low oxygen can contribute to breathing difficulty, lethargy, appetite loss, skin damage and abnormal swimming.

Are these fish disease guides a veterinary diagnosis?

No. They provide educational information and possible explanations. Diagnosis and medication decisions should be confirmed by a qualified aquatic veterinarian or fish-health professional where possible.