Stress in fish – Find The Causes

Like all living things on the planet, fish can be stress.

For them, however, stress is a much more serious problem. In most cases, fish mortality in an aquarium is directly or indirectly due to excessive stress caused by poor water quality, inappropriate aquarium neighbors or rapid environmental changes. When fish are stressed, they become more susceptible to a wide range of ailments and diseases. In other words, stress can kill fish.

Stress often goes unnoticed in an  aquarium, so it’s important to be aware of its symptoms.

Look for fish that:
are lethargic or tired; Trying to jump out of the water; restlessly rushing about in the aquarium; are at the surface of the water and breathe heavily; not as bright as usual; look emaciated, have ragged fins or tails; behave strangely; refuse to  feed.

If fish show symptoms of stress, it is imperative to find the cause.

stress fish

Ask yourself simple, clear questions. Have you recently placed fish in your aquarium that might not get along well with others? Have you changed the temperature or quality of the water? Does the aquarium have an air pump? Forgot to change your aquarium water? Have you changed the amount of light or the type of lighting in  your aquarium?

Change Of Condition

Any changes in the conditions of keeping fish in the aquarium are of great importance. It would seem that a slight change in water temperature by only 2 degrees can cause a temperature shock, which, in turn, will cause stress and, in the end, kill the fish.


In addition, you need to know that poor nutrition, cleaning the aquarium too often, using a fish net and especially inept actions are extremely dangerous. Always use two nets and avoid chasing fish in the aquarium. To do this, use a small landing net to gently guide the fish into the large one.


If you have not made any changes to the aquarium lately, the water temperature is OK, it is best to analyze all possible causes of stress in stages.


Contamination or toxins. Make sure that the level of ammonia or nitrite / nitrate in the water does not exceed the acceptable level. Change the water and replace the  aquarium filter.

pH Value

The pH value for freshwater fish is from 6.0 to 9.0 and for marine fish is 8.2 to 8.3. If the water quality does not meet these requirements, slowly adjust the pH value to that required for freshwater fish using  chemicals that regulate the alkalinity or acidity of the water. For saltwater fish, adjust the salinity of the water, which will change the pH value.


If the aquarium has temperature problems, gradually adjust the thermostat , changing the water temperature to no more than one degree per hour. Also, make sure that the lighting in the aquarium does not heat up the water. Do not place fish in the same aquarium that differ in temperature by more than 4 degrees.

Before adding new fish to the aquarium, keep them at the top of the aquarium in a bag of water from the container they were in before until the temperature of the water has evened out.


According to rough estimates, freshwater fish with a length of 2.5 cm need 5 liters of water, and for sea fish with a length of 2.5 cm – up to 10 liters of water. If the aquarium is overcrowded, get another one and divide the fish. If you prefer to keep all the fish together, consider purchasing a larger aquarium.


If you have eliminated chemical stressors, add some embellishments to make sure the fish species in your tank are compatible. Place incompatible fish in different tanks. 

Aeration and strong water circulation

Make sure the filter fits the size of your aquarium. Adjust the water flow so that it does not lift the contents from the bottom of the aquarium, which will significantly reduce the oxygen level.


Make sure your fish are not malnourished. Diversify their diet, try new food, add vitamins if necessary.

fish stress

Stress in fish is not an easy situation

You can try to treat the diseases caused as a result, however, unless you eliminate the source of stress, the fish will not regain their health. As with most diseases, preventing stress is better than treating it. 

Knowing the symptoms of stress and understanding the causes that cause it is the first step in maintaining the health of your aquatic pets.


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