Causes of Fish Stress

I’m sure that many of us have enough stress in our lives that we laugh off the thought of our fish being stressed. But a stressed fish is all too often a soon-to-be sick fish. A fish that is stressed has a weakened immune system and is thus much more susceptible to attack from parasites, bacteria, or other pathogens. Ensuring that your fish are under as little stress as possible is the best thing you can do to ensure a long and healthy life for your friends with fins. This list of the 10 most common causes of fish stress may help save your fish. (And if you still laugh off the thought of fish stress just remember that if your fish begin to die, that is one more stress factor in YOUR life).

1. Sudden changes in pH. pH will always fluctuate to some degree, but we want to have a pH that is as stable as possible. Ensuring that the buffering capacity (KH) will help keep a stable pH level. pH that is too high or too low can also cause stress, but stability is what is most important.
   
   
2. Sudden changes in water temperature. Goldfish and koi are cold-blooded and can tolerate a wide range of temperatures, but a sudden change in that temperature can cause undue stress. Proper acclimation when adding new fish is critical. Small, shallow ponds are more apt to have the water temperature change quickly. Providing good surface coverage will help keep the temperature changes slow.
   
   
3. Insecurity. Fish can be stressed if they are not comfortable in their surroundings. Clear water with little surface coverage will cause a fish to feel insecure. The fish are more susceptible to predator attack in clear water and the fish is aware of this risk. Providing surface coverage or an underwater hiding place can help. Extra stress will be caused if the fish have actaully been visited by a potential predator.
   
   
4. Poor diet. Fish need a regular balanced diet. This is not as complicated as it may sound. While some packaged foods may have advantages over other, as long as they are getting a regular feeding of a seasonally-appropriate food labeled for koi or goldfish they should be getting the nutrient they need.
   
   
5. Poor water quality. Water quality is a broad term but is often referring mainly to the nitrogen compounds found in the water. Ammonia, Nitrite, and Nitrate are always going to be present to a degree in a pond with fish, but the levels need to be kept as low as possible. Good filtration is the key to breaking down ammonia and nitite. Nitrate is used up by plants or should be removed with regular, partial water-changes.
   
   
6. Water toxin. There can be many, many possible toxins coming from many sources that can stress or directly kill fish. Chlorine and chloramines are common additives to tap water that if not removed can cause severe stress or death. Other common sources for toxins are lawn fertilizers or pesticides that may blow into the water or be washed in along with rain. If this type of toxin is suspected an immediate water change would be called for.
   
   
7. Lack of sufficient oxygen. Fish rely on dissolved oxygen in the water for respiration. Common causes of a low disolved oxygen level are too many fish, not enough aeration, or a large algae kill.
   
   
8. Overcrowding. Keeping too many fish leads to many of the other issues addressed here including poor oxygen levels and buildup of nitrogen compounds.
   
   
9. Physical stress. Physical stress can be caused by an actual wound. A fish can be wounded by a predator or scrape against a sharp rock in the pond. Handling a fish also will cause stress. Avoid catching fish unnecessarily.
   
   
10. Infection. Stress may lead to an infection from some sort of pathogen, but an infection will also increase the stress level thereby making the fish more susceptible to further infection and limting their ability to fight it off.

You may also be interested in our article on Guarding Against Sick Fish.