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Is Your Pet Fish Stressed?

fish care

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Just like humans, fish experience stress too. When fish are stressed, it can have negative effects on their appearance and health. Fish stress can weaken their immune systems, increasing the risk of disease and even death. While fish do experience stress in the wild, it is the most common cause of health issues in aquarium fish. Luckily, through proper fish care, you can reduce most stress factors in your aquarium and prevent having a sick fish.

What Is Fish Stress?

“Stress is a term we use in vet medicine to describe any condition in the environment that causes the release of cortisol and adrenaline in the body,” said Dr. Julius M. Tepper, DVM, Certified Aquatic Veterinarian and fellow at the World Aquatic Veterinary Medical Association in Stafford, England. “These substances are associated with the ‘flight or fright’ reaction and help the animal cope with the stressor.”

When the cause of the stress is continuous, like poor water quality or harassment from other more aggressive fish, the normal immune functions are blocked, which often leads to sick fish with disease conditions like parasites, bacterial infections and fungi, says Dr. Tepper.

What Causes Fish Stress?

Some of the most common causes of fish stress in aquariums include:

  • Elevated ammonia and nitrate levels due to infrequent water changes, which is the main cause of stressed goldfish
  • pH fluctuation due to the exhaustion of mineral buffers
  • Fluctuations in water temperature, which is the main cause of stressed Betta fish
  • Lack of hiding places to relieve stress
  • Aggressive fish in the same tank
  • Overstocking the aquarium, which leads to poor water quality and less oxygen
  • Improper introduction of new fish into a community tank
  • Inadequate tank size
  • Poor nutrition or irregular feeding routine

What Are Stressed Fish Symptoms?

To help reduce fish stress, it’s important to know what to look for. Observe your fish often and watch for any change in your fish’s routine behavior, such as the following:

  • Hiding for long periods of time
  • “Flitting” or darting around the tank
  • Frantic swimming; crashing at the bottom of the tank
  • Gasping for air at the surface (a sign of low oxygen levels)
  • Scraping against rock or gravel
  • Loss of appetite

Stress can also affect your fish’s appearance. Look for changes like:

  • A decrease in coloration, especially if your fish is brightly colored
  • Red streaking in fins
  • White spots on the body, which can be a sign of Ich
  • Any visible ailments or sores

If you notice any change in behavior or appearance that may be indicative of a sick fish, consult your veterinarian.

Ways to Reduce Fish Stress

The best way to prevent or reduce fish stress is to provide them with a healthy environment. That includes stocking the tank with the right amount of aquarium decorations and having the proper aquarium supplies. You want to ensure that they are receiving the proper fish care that minimizes triggers.

  • Change water frequently to keep nitrate and ammonia levels low. Try adding water conditioners like API Stress Coat Aquarium Water Conditioner, which is formulated to reduce fish stress by 40% by removing dangerous toxins. Or try API Stress Zyme Aquarium Water Conditioner, which keeps your aquarium cleaner and helps boost its natural cycle.
  • Check water temperature for consistency regularly to prevent stressful fluctuations.
  • Provide an optimal filtration system like the Fluval Underwater Filter that captures debris and bacteria while ensuring proper oxygenation.
  • Provide hiding places, like the Marina Mangrove Root Aquarium Decor, but be careful not to overcrowd your tank, which can interfere with proper oxygen flow.
  • Before you add fish to your community, ensure they are compatible with your current fish to prevent stress from harassment or fighting.
  • Introduce new fish properly, preferably by immersing them in the tank while still in their plastic bag, to help them adjust to the water temperature, and for your current fish to get used to their new tank mate.
  • If you notice harassing behavior, remove the aggressive fish and place in a separate tank.
  • Give your fish adequate space; the general rule is a fish of 1 inch length needs 1 gallon of water.
  • Feed them proper amounts of food regularly, and if possible, at the same time of day.

By providing a healthy, stable aquarium environment and observing your fish for any signs of behavioral or physical change, you can reduce the risks of fish stress and keep a healthy, serene tank.



Chris Brownlow has been writing about pets for over 10 years. As a writer who believes in immersing herself in her topic, she has tasted more than 20 different flavors of dog and cat food while working on an advertising campaign for PetSmart. Prior to her pet days, Chris was a print and digital journalist at The Tampa Tribune and The Virginian-Pilot.