Merck Manual

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Pet Owner Version

Emergencies of Fish


Ruth Francis-Floyd

, DVM, DACZM, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida;

Barbara D. Petty

, DVM, North Florida Aquatic Veterinary Services

Last full review/revision Feb 2020 | Content last modified Oct 2020

Most home aquarium and pond emergencies are not truly medical in nature. They generally involve something going wrong with the aquatic environment such as a leak or an electrical problem with a heater or pump. In many cases, fast action can resolve the emergency. Make sure that all electrical items are grounded or have a circuit-breaking function along the power line. The possibility of leaks and spills, and their consequences, can also be lessened through planning and quick action.

Most emergencies can be avoided by planning and vigilant monitoring of the environment through water tests. Sudden releases of toxins (for example, chlorine, ammonia, or nitrite) from old activated carbon and certain water treatment chemicals may be identified ahead of time, or at least before they become fatal. Unfortunately, emergency medical treatment for pet fish is not as advanced or as readily available as it is for dogs and cats. If a veterinarian with fish experience is nearby, some instances of physical trauma to fish, such as an outdoor koi being attacked by a wild animal, can possibly be treated.

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