Stress in Aquarium – Complete Guide to Aquarium Fish Stress and Solutions

Stress is dangerous for you as well as for your fish. Since stress causes the immune system to weaken in fish, it is a situation that needs great attention. Even short-term stress can have terrible effects.

The stress experienced in fish can cause various diseases and deaths. Excessive stress experienced by the pet causes their respiratory rate to increase and they want to get rid of the stress as soon as possible. Inability to get rid of stress can lead to chronic diseases. It is possible to treat certain stress levels in the pet. However, it should be kept in mind that high levels of stress can be fatal and necessary precautions should be taken.

What Causes Stress in Pet Fish?

Stress can be defined as the physiological and psychological effect of bad conditions on living things. The stress in pet is basically caused by the aquarium not being properly arranged for them. Studies on the subject have revealed that fish have a very strong immune system and adapt much more easily in new environments than other living things. However, if the ecological system we have set up with great efforts in our homes for aquarium fish is insufficient for any reason, each point that causes this will be a stress factor. The better the habitats of the fish in nature are imitated, the less likely they will be stressed. While creating a visual world for yourself in your home aquarium, you should take care not to make mistakes that will stress your pet.

Main Causes of Stress in Aquarium Fish:

  • Under-sized fish tank
  • Unsuitable pH level
  • Unfavorable temperature
  • Unstable water temperature
  • Improper oxygen amount
  • Unsuitable water hardness
  • Too many fish in the tank
  • Sudden changes in water chemistry
  • Excessive use of medication and water conditioners
  • High nitrate level
  • High ammonia level
  • Aggressive fish in the tank
  • Not enough hiding space in the fish tank
  • Poor feeding diet
  • Continuous and high lighting contrary to nature

Different Species in the Same Aquarium

Different fish species in the aquarium can get stressed out by not communicating with each other. Because some fish species move very fast and suddenly, while others move slowly. This difference in movement in pet will cause them to be anxious and stressed. Again, sharing the same environment of fish species that are not from the same habitat may cause stress for anyone. However, although they are from the same habitat, there may be fish with different temperaments. A type of constantly aggressive attitude will disturb and stress those who are more docile. For this reason, when choosing fish for the aquarium, species that are compatible with each other should be preferred.

In addition to these, fish that pair with a pair may exhibit more aggressive attitudes than others. In this case, other fish will be under stress. In order to prevent this, it would be much more appropriate to look at the spouses in a separate environment.

Poor Feeding Diet

Feeding your pet in an aquarium has two aspects in terms of stress.

First of all, if you do not feed the amount and variety to meet the needs of your pet in the aquarium, your fish will be stressed due to unbalanced and insufficient nutrition.

Even if you feed more than necessary, your fish will be stressed as you will disrupt the water quality. You should do the necessary research to provide the nutritional diet that will meet the needs of your fish and you should not give more feed than your fish will consume in 3-4 minutes.

Under-sized Fish Tank

Like all living things, fish also need spaces. Being in a smaller area than the fish needs will cause them to be stressed. When setting up your aquarium, you should plan the fish species and numbers according to the size of your aquarium. In overburdened aquariums, it will be difficult to maintain the necessary water quality and cleanliness and will cause stress to the fish.

Unstable Water Temperature

All aquarists buy heaters for their aquariums. However, using the heater properly requires experience. One of the functions of the heater is to keep the water temperature constant. There are thermostat heaters to provide this. Buying a quality heater with a thermostat for your aquarium will reduce the stress on your fish. You may also want to take a look at our “How to Choose the Right Fish Tank Heater? Complete Aquarium Heater Guide” article.

High Nitrate and Ammonia Level

Nitrate and ammonia levels in aquarium water are critical. Especially in newly established tanks, sudden increases in these values can be observed due to the low number of beneficial bacteria. It is important that you do not add fish until you are sure your aquarium is cycled. After the newly established aquarium is cycled, gradually adding the planned number of them to the aquarium can be preferred to balance the nitrate and ammonia levels.

You may want to see our article about Beneficial Bacteria In Aquarium | Nitrogen Cycle

Poor Aquarium Conditions

Poor water conditions are one of the important factors that cause stress in them. Particular attention should be paid to the hardness, cleanliness, and pH values โ€‹โ€‹of the water. For this, it is necessary to obtain information about the hardness and temperature of the water that the fish species kept in the aquarium need. Again, aquarium lighting should be done correctly. If more than one lamp is used for the aquarium, the lights should be turned on gradually, not all at the same time. Otherwise, the sudden light will create stress for the fish. Higher intensity light is used in aquariums where plants are fed. In this case, shady areas should be created for fish. Again, the light being on all night causes the fish to be stressed. Because they also sleep to gather energy and keep their metabolism strong. Some fish, on the other hand, wander at night and cannot be comfortable in constant light conditions.

Aquarium floor material can also cause stress to the fish. Because some fish form their breeding areas and hiding areas by shaping the sand and they spend a significant part of their time under the sand. For this reason, a base material with properties suitable for the fish species should be preferred. The aquarium decor should be compared to natural habitats as much as possible. Thus, areas, where fish can be alone and reproduce, are created. Aquarium rock decor, various plants, and logs can be used for this. In addition, excessive circulation in the aquarium causes the fish to get tired and stressed. For this reason, a suitable aquarium filter and wave motor should be preferred for the aquarium.

Reasons such as malnutrition, the presence of many fish in the aquarium, excessive drug use, loneliness, and changing the aquarium can also cause stress in fish.

External Factors

Fish are creatures easily affected by external factors. The most important external factor is human. For this reason, the more isolated the aquariums from the external environment and the less intervention in the aquarium, the more stress the fish are. Fish are disturbed by external movements. For this reason, the aquarium should be positioned in areas away from movement instead of middle areas open to external movements.

Another external factor that causes stress in fish is high-intensity sound. For example, high-intensity sound systems can cause stress. In addition, these sound systems not only cause noise but also vibration, and vibration has a negative effect on fish.

What Are Stressed Aquarium Fish Symptoms?

  • Strange swimming
  • Breathing on the surface
  • Feeling the constant need to hide
  • Discoloration
  • Decreased appetite
  • Fast swimming
  • Lethargic behavior
  • Reduced fitness
  • Rapid gill movements

How to Reduce Aquarium Fish Stress?

To understand that fish are experiencing stress, first of all, the characteristics of the fish species should be known. For example, herd species choose to leave their herd and be left alone when stressed. Again, stress symptoms in fish can also be counted when they start to move abnormally. In this sense, abnormal situations such as sudden movement, constantly stopping at a certain point, or constantly opening and closing its mouth can also be a sign of stress.

If you want to be sure your fish don’t experience stress, it’s important to the fish for your aquarium from reputable sources. In case you’re not sure about the health of a new fish, you can use a quarantine aquarium to monitor it before you put that fish with the rest from your tank. Once you’re confident the fish is healthy, you can move it to the main aquarium. Additionally, it’s crucial to maintain high water quality, provide appropriate feeding, and good conditions in your aquarium according to the species of fish you have.

In addition, we mentioned that adding new fish to the aquarium or using drugs causes stress to them. In such cases, fish stress-relieving products can also be used so that the fish relax and do not experience stress. These products can be used in fresh and saltwater aquariums; They do not harm plants, reef creatures, and beneficial microorganisms and do not cause any changes in the pH level of the water.

As a result, it is possible to cure stress in pet. However, it is much easier to always be a good observer and take the necessary precautions than to return a fish that has been eroded by stress to its normal life. For this reason, the fish should be made aware of the factors that cause stress and they should be kept away from these factors.


A small amount of stress can be beneficial for any living being, but too much stress is definitely harmful. You should take the necessary precautions to prevent your pet from getting stressed. If your fish is under stress, you should identify the source of the stress and eliminate this situation.

๐Ÿ ๐™ƒ๐™‹ Team
๐Ÿ ๐™ƒ๐™‹ Team
We're just like you - aquarium enthusiasts who love aquatic life! We've been caring for and breeding all sorts of freshwater and marine aquarium fishes, plants, and other pretty little creatures for years. We love sharing our knowledge with other fish hobbyists, and this article you have just finished reading is the best proof of that. You can read more about us here.

Related Articles


Please enter your comment!
Please enter your name here