An aquarium is a magical world full of life, but often you may face a disappointing phenomenon: your fish don’t survive. Why does this happen? There are various reasons that can lead to such an outcome, and in this article, we’ll analyze the most important ones.

Poor Water Quality

Water quality is vital for the health of fish. If it is not suitable, fish can experience stress, disease, and ultimately may not survive. The conditions of the water should mimic the natural environment of the fish as closely as possible to avoid any disruption to their metabolism and respiration.

Key Factors Affecting Water Quality

• Ammonia, Nitrites, and Nitrates: These toxic substances result from fish waste, decaying food, and rotting plants. Without proper biological filtration, their levels can rise dangerously, harming the health of the fish.
• pH and Hardness: Each fish species has specific requirements regarding the water's pH and hardness. If the pH is too acidic or too alkaline for a certain species, it can cause serious problems for their gills and skin.
• Lack of Oxygen: If the water is not properly aerated, oxygen levels may drop, making it difficult for fish to breathe, causing lethargy and making them more susceptible to disease.

How to Keep the Water Clean

• Perform regular water changes (at least 20–30% weekly) to remove toxic substances.
• Use appropriate filters for mechanical, chemical, and biological filtration.
• Frequently check water parameters with special tests and adjust them as needed.

Overpopulation in the Aquarium

One of the most common mistakes made by beginners is overstocking the aquarium with more fish than the system can support. This creates problems in both water chemistry and fish behavior.

Problems Caused by Overpopulation

• Increased Water Pollution: More fish means more waste production. This raises ammonia and nitrate levels, overburdening the biological filter.
• Oxygen Shortage: An excessive number of fish increases oxygen consumption, especially if aeration is inadequate.
• Stress and Aggression: Fish need space to swim and establish their natural social structures. Overpopulation can lead to stress, aggression, and increased competition for food and shelter.

Solution

• Research how many fish can comfortably live in the size of your aquarium.
• Follow the general rule: one centimeter of fish body length per liter of water (though this depends on the species).
• Don’t add too many fish at once, so that the biological filter can gradually adjust.

Inappropriate Living Conditions

Not all fish are suitable for every aquarium. Some species have very specific requirements, and if these are not met, stress and weakened immune systems are inevitable.

Mistakes That Lead to Problems

• Mixing Fish With Different pH and Temperature Needs: A fish that prefers acidic water cannot easily coexist with one that needs alkaline conditions.
• Housing Aggressive Species With Peaceful Fish: Some species, such as cichlids, are more aggressive and cannot live peacefully with calm fish like guppies or neon tetras.
• Lack of Proper Hiding Spots and Decoration: Most fish need natural shelters like plants, rocks, and driftwood to reduce stress and feel safe.

What to Do

• Study the needs of each species before adding them to the aquarium.
• Create a natural environment with plants and appropriately arranged areas for each species.
• Ensure that all fish have enough space to move freely.

Poor Nutrition

Nutrition plays a vital role in the health of your fish. An improper diet can lead to digestive problems, weakness, and diseases. Nutritional needs vary from species to species, and using the wrong type of food can have serious consequences.

Common Feeding Mistakes:

• Overfeeding: Fish will eat as much as they are given, but excess food dissolves and pollutes the water.

• Wrong type of food: Some fish need a protein-rich diet, while others require plant-based nutrition. Generic fish food may not meet their specific needs.

• Lack of variety: A monotonous diet can lead to nutritional deficiencies.

Tip:

• Feed small amounts 2–3 times per day.

• Use a variety of foods: dry, frozen, and live, depending on the species.

• Observe consumption and adjust the quantity accordingly.

Diseases and Parasites

Like all living organisms, fish are prone to illnesses. The most common ones are bacterial infections, fungal diseases, and parasitic infestations.

Signs Your Fish May Be Sick:

• Loss of appetite

• Abnormal behavior (e.g., rubbing against surfaces)

• White spots or wounds on the body

Prevention: Maintain high water quality, avoid stress, and quarantine new fish before introducing them to your aquarium.

Stress and Sudden Changes

Stress can be fatal to fish. Changes in their environment without proper acclimation can shock them and lead to death.

Causes of Stress:

• Sudden temperature changes

• Excessive lighting

• Frequent disturbances in the aquarium

What to Do: Gradually acclimate new fish and maintain a calm and stable environment.

Maintaining a healthy aquarium requires care and knowledge. If you’re wondering, “Why aren’t the fish surviving in my aquarium?” consider all the factors mentioned above. With proper management and attention to detail, you can keep your fish healthy and happy.

At aquariumshop.gr, you’ll find everything you need for a healthy and balanced aquarium—from equipment and filters to specialized foods and water care products. If you have any questions or need advice on proper fish care, our experienced team is always available to help. Don’t hesitate to contact us for any information!