Sudden Death of Pond Fish

Pond fish are remarkably resilient animals and are quite hardy in most conditions; however, they can and do die suddenly if water conditions are not maintained or they are exposed to an infection. Testing and adjusting your water and performing a daily visual inspection of your fish will reduce the likelihood your fish dying.

  1. Sores/Infections

    • Untended sores or ulcers can cause sudden death in pond fish. These are more common during the winter months, when fish spend more time along the bottom of a pond that is lined with stones. The scales on the underside of the fish will rub against the rocks and can create sores that will fester and become infected, killing the fish.

    Water Quality

    • A buildup of nitrites and ammonia from excessive fish waste will also cause your pond fish to die. To prevent this condition, refrain from overfeeding your fish, and establish a good biological filter, which will convert harmful nitrite and ammonia into harmless nitrate.

    Chlorine/Chloramines

    • Chlorine and chloramines will kill your fish by causing gill burn. This occurs when an unwitting pond owner introduces untreated tap water into the pond. A dechlorinator should be used on all water before being introduced into the pond.

    New Fish

    • New fish can carry infections that can kill your other fish. Quarantine new fish for several weeks before introducing them into your pond to check for signs of infection.

    Oxygen Levels

    • Decreasing oxygen levels will also cause fish in a pond to die. Dissolved oxygen levels will drop when there is an excessive amount of organic material in the pond that has to be broken down, such as leaves, grass clippings and algae. Also, warmer water tends to be less oxygenated than cold water. Adding a bubbler to your system and regularly cleaning the bottom of the pond should alleviate this problem.