“Shock” and “Stress” in aquarium fish

Shock and stress is the physiological response of fish to adverse stimuli (e.g. inappropriate environmental factors). Among aquarists, shock and stress are usually seen as a short-term and long-term reaction, although shock can be perceived as an extremely acute form of stress.

For all higher organisms, experiencing this or that degree of stress during life is a completely normal phenomenon. However, under certain circumstances, long-term (chronic) stress can be a serious health hazard. In an aquarium, stress should be avoided whenever possible, especially when it comes to those fish whose health is already at risk (for example, due to illness or injury, as well as after transportation).


This is the physiological reaction of the body to sudden shocks of various types – usually to too abrupt changes in one or more environmental factors. The causes of shock can be completely different – nitrate shock, osmotic shock, pH shock, temperature shock, etc.


May be different – depending on the nature and severity of the damage. Among them may be the following: a decrease in the color intensity; accelerated or slowed breathing; lying on the bottom (a very common symptom) with periodic sharp movement to another place; In addition, fish hide among plants or other decorative objects. Sometimes the shock manifests itself in the form of flight, and then the fish frantically rush around the aquarium up, down, and along the walls, as if trying to find a way out. In severe cases, fish can lie on their sides or even belly up. Death from shock is a fairly common occurrence, especially among sensitive fish!

If you want to know how temperature shock looks, watch this video. Accidentally cold water was poured instead of warm: Be careful video has SOUND!

Temperature shock with water change =(


Sudden changes in one or more environmental factors. Most often, a shock is observed in fish just launched into the aquarium, but it can also be observed with a partial change of water, especially if not enough attention is paid to the correspondence of the parameters of new water and water in the aquarium. Exposure to shock is different in fish of different species and different individuals.

Even in the absence of significant changes in water parameters, fish experiencing severe stress can exhibit shock symptoms when they are first launched into the aquarium, especially after transport. This is their reaction to an unfamiliar environment. This syndrome is sometimes called “shock after launch” or “stress after transport.”


Fishes should not be exposed to sudden changes in water parameters, as well as any type of poisoning. When using chemical drugs, especially in the form of short-term baths with a high dose of the drug, fish should be constantly monitored and monitored to see if they show signs of shock. If necessary, the procedure should be discontinued.


If the shock begins quickly and clearly (for example, in the case when it is caused by a sharp change in temperature or acute poisoning), you should first establish its cause (to do this, check the water parameters), and then immediately correct the situation. If all the inhabitants of the aquarium are affected (for example, when the reason for the shock is a rash change of water), the conditions in the aquarium should be changed. If, due to the unusual parameters of the water, new fish recently launched into the aquarium are affected, they should be transferred to more suitable conditions, that is, into the water with the parameters that are familiar to them. Do not change the chemical composition of the water in the main aquarium so that it is suitable for new fish, as this will cause a risk of shock to those fish that already live in the aquarium!

If new fish that have just been launched into the aquarium are shocked by the transport and unfamiliar surroundings, they should be left alone so that they can adapt to their new position and recover from stress. They can not be poked or shoved, trying to force them to leave the shelter, and if they are at the bottom, you can not force them to swim, since this additional stress can cause fatal consequences. In such cases, it is useful to turn off the light in the aquarium before the next day, as the period of darkness has a calming effect on many fish. By that time, most of the fish will recover and join the new environment.


Stress is a serious problem for aquarium fish. Chronic stress usually ultimately ends in death – for example, from slow exhaustion or due to reduced immunity, and therefore increased vulnerability to infections. Unfortunately, its effects are often underestimated or attributed to other causes (for example, some imaginary infectious diseases).

Stress is undoubtedly an integral part of the life of fish in nature. In particular, fear of predators can serve as a prime example of natural stressors. However, in the close framework of the aquarium, numerous stressful situations often arise that in nature either does not occur at all, or fish can easily escape them by swimming away to another place with more favorable conditions.

Aquarium fish shock and stress


The signs of stress are numerous and nonspecific, so the diagnosis is most often made on the basis of circumstances, that is, a known possible cause of stress – for example, when other fish pick up the fish or there is a large amount of nitrate in the water. Among these symptoms, the following may be present: loss of appetite and, in the long term, gradually developing exhaustion; the desire to hide, including standing in the corners of the aquarium head up or down; nervousness and a tendency to panic (“pancakes” on the surface of the water, jumping, finding a way to escape through the glass of the aquarium); abnormal color (usually much darker, and sometimes paler than normal); rapid breathing.


Environmental factors – inappropriate chemical composition of water; poor water quality; inappropriate temperature; unsuitable shelters or insufficient numbers; aggression from other fish or fear of aggression from larger or brighter neighbors in the aquarium (even if in fact they are peaceful and harmless fish); external irritants – for example, a knock on the glass of an aquarium; constant or unusual activity near the aquarium, loud noise and the accompanying vibration.

In addition, diseases in themselves can be stressful factors, like some drugs and the treatment process itself. Caring for the aquarium (with the exception of the case when it is done carefully and calmly) can also cause stress in the fish: constant changes in decoration and other “trivia”, even if this is done with the best of intentions. If fish is picked up, especially when caught in a net, packaged or transported, it is always a source of stress. Even breeding in many fish can cause stress. The source of stress can be stalking (which is sometimes part of the courtship ritual) because the fish have no way to hide from a persistent but unwanted fan within the confines of the aquarium. Fish of those species that take care of their offspring can, during spawning, perceive their neighbors in the aquarium, which are usually quite acceptable, as a terrible threat to their brood, and because of this experience stress (while causing it to other fish).


It is probably not possible to completely avoid any stress in aquarium fish. However, every effort should be made to provide them with a stress-free environment by creating suitable living conditions. To do this, you need to properly select the water of the proper chemical and physical parameters, decoration, neighbors in the aquarium, food, etc. The external causes of stress resulting from human activities should also be minimized. The aquarist should constantly be vigilant, regularly, and carefully monitor his fish and look for any signs of stress or its potential causes.


Establish and eliminate the cause (s) of stress. Sometimes this means that you have to find another home for the fish if they were incompatible with each other. Remember that the best solution to the problem of fish aggressiveness most often consists in the following: it is easier to get rid of one single badass fish than to multiply the number of its victims.

You can also watch this video, explaining fish stress in video format: Be careful video has SOUND!

7 Ways To Reduce Stress On Aquarium Fish

Aquarium free of shock and stress is the hallmark of a skilled aquarist!