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Anyone who owns a home aquarium knows that fish are not only easy-to-care-for pets but also sensitive creatures that require special attention. Just like all animals, fish can get sick, which is often noticeable through changes in their behavior, appearance, or environment. But when exactly should one take a sick fish to the vet? Here are some hints and tips to ensure the well-being of your scaly friend. 

1. Noticeable Behavior

If a fish suddenly starts behaving differently – whether it stays isolated, remains at the water’s surface, lies at the bottom, or swims uncontrollably – this could be a sign of illness or injury. 

2. Physical Changes  

Bubbles, discolorations, fin rot, or other visible anomalies on the fish’s body can indicate health issues. Similarly, swollen eyes or a bloated belly can be signs of an illness. 

3. Loss of Appetite    

A healthy fish usually has a good appetite. If you notice that a fish refuses food over several days, you should be cautious. 

4. Water Condition  

The water in an aquarium can provide many clues to potential issues. Cloudy water, sudden temperature fluctuations, or a changed pH level can cause stress or diseases in fish.

Goldfish sideview
image: Hans –

When should you see a veterinarian? 

If you notice one or more of the symptoms mentioned above in your fish and, despite adjustments in the aquarium (such as water changes or feeding modifications), no improvement is observed, it’s time to consult a veterinarian. A vet specializing in fish will be able to provide an accurate diagnosis and recommend appropriate treatment.

Prevention as the Key to Your Fish’s Health

Preventing diseases isn’t only crucial for humans or land animals but also for our aquatic dwellers. A well-maintained aquarium can make the difference between a healthy fish and a sick one. Here are some detailed tips to effectively prevent diseases in your home aquarium:  

1. Cleanliness of the Aquarium: 

A clean aquarium is the foundation for your fish’s health. Dead plants, excess food, and other debris should be regularly removed to prevent the growth of harmful bacteria and fungi. Regular water changes are also crucial to remove toxins and introduce fresh water. 

2. Monitoring Water Values: 

Water is the lifeblood of your fish. Therefore, it is essential to regularly check water parameters such as pH, ammonia, nitrite, and nitrate. Unbalanced water can lead to stress and diseases in fish. There are specialized test kits available that allow you to check these values at home. 

3. Quarantine for New Fish: 

Before introducing new fish into your main aquarium, it’s wise to first place them in a separate quarantine tank. This gives you the opportunity to inspect the new fish for signs of diseases or parasites and ensure they are healthy before they come into contact with your existing fish. A quarantine tank helps prevent the spread of diseases and also offers a safe space for sick fish to recover without stress from others. 

Goldfish in round fish tank

4. Educate Yourself About Fish Diseases: 

The more you know about the various diseases that can affect fish, the better prepared you are to detect signs early and take appropriate action. 

Overall, prevention is the best way to ensure the well-being of your fish. With regular care, attention, and a proactive approach, you can ensure that your aquarium provides a safe and healthy environment for all its inhabitants. 


Fish are delicate creatures that require careful attention at the first sign of illness. With a watchful eye and regular maintenance of your aquarium, you can prevent many problems. However, if you think something is amiss, don’t hesitate to seek advice from an expert. Your fish will thank you! 



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