How to Handle Stress in Aquarium Fish

It may seem like they live a care-free life, but aquarium fish can suffer from stress. Here’s what you need to look for and what to do if it happens to your fish.


Like any other animal, aquarium fish are prone to stress if their conditions are less than ideal. If you do not keep your aquarium clean, or if you fail to meet the nutritional needs of your fish, they are likely to become stressed. When that happens, your fish have an increased risk for succumbing to disease. In order to protect your fish and to keep them healthy you should learn to identify the signs of stress and learn how to deal with it.


Signs of Stress in Fish


Different animals show stress in different ways, but the biggest indicator of stress in fish is changes in behavior. If one of your fish suddenly starts rubbing its body against objects in the tank, or if it starts lolling on the bottom of the tank when it usually swims near the surface, it could be an indication of stress. Other symptoms of stress in fish may include:


  • Lethargic behavior
  • Rapid swimming around the tank
  • Decrease or loss of appetite
  • Rapid gill movement
  • Darkened coloration
  • Loss of condition or pattern
  • Hiding in the tank
  • Gasping for air at the surface


The symptoms your fish expresses will be a reflection of the cause of its stress. For example, if something is affecting the oxygen levels in your tank, your fish will likely show signs of breathing problems.


Related: 4 Most Common Mistakes New Aquarium Hobbyists Make


Causes of Stress in Fish


Because an aquarium is an enclosed environment, many changes to that environment can have a big impact on your fish. Any change in water temperature, quality, or chemistry could be dangerous for your fish and could induce signs of stress. It is also possible for your fish to become stressed when the conditions in your tank are healthy, but they aren’t the right conditions for the specific fish you are keeping. Other causes of stress in fish may include the following:


  • Sudden change in water temperature
  • Reduction in water quality
  • Changes in water chemistry levels
  • Elevated ammonia levels
  • High nitrate or nitrite levels
  • Too much salt in the water
  • Low oxygen levels
  • Bullying by other fish
  • Lack of hiding places for fish
  • Small tank or overcrowding
  • Tank lighting too bright
  • Use of medications or water treatments
  • Improper or inadequate diet
  • Addition of new fish to the tank


To put things in the simplest terms, any change to your tank environment is a potential source of stress for your fish. The bigger the change, the more stressed your fish are likely to become.


Related: Setting a Schedule for Routine Tank Maintenance


Tips for Dealing with Stress


In order to de-stress your fish, you need to identify the cause of their stress. If you don’t see anything physically wrong with the fish or with the tank, perform a water test to check for changes in water chemistry – you should also check the tank temperature and make sure that your filter and other equipment is working properly. If you are dealing with a problem in water quality, performing a water change is the first step you should take. This should also remedy minor problems with water chemistry that could be affecting your fish. If you suspect that an illness is causing the stress for your fish, try to identify the symptoms then make a diagnosis and start the proper treatment.


Many aquarium fish species are capable of adapting to minor changes in tank conditions but some are more sensitive than others. All fish are susceptible to stress and chronic stress can be deadly. The sooner you notice the signs of stress in your fish, the sooner you will be able to identify the cause and remedy the problem.

Kate Barrington
Kate Barrington

Kate Barrington is the loving owner of two cats (Bagel and Munchkin) and a noisy herd of guinea pigs. Having grown up with golden retrievers, Kate has a great deal of experience with dogs but labels herself a lover of all pets. Having received a Bachelor's degree in English, Kate has combined her love for pets and her passion for writing to create her own freelance writing business, specializing in the pet niche.

More by Kate Barrington

Popular Pet Guide
Next