A question usually posed by beginners, even experienced saltwater aquarium hobbyists are sometimes stumped as to the reason a fish in their tank has died.
Normally, an alert aquarist can see the symptoms (frayed fins, cloudy eyes, unusual behavior, water test results) of a problem before a death occurs, but ocassionally a fish will die suddenly with no apparent reason. Barring the possibility of a fish becoming infected and dying from the West Nile Virus, below are the most probable reasons for a tank critter to die.
- Ammonia Poisoning
- Occurs most frequently while cycling a new tank, but also happens during collection or while in transit.
- If the tank has been fully cycled for a period of time, New Tank Syndrome may be the cause.
- Symptoms include cloudy eyes, frayed fins, rapid gilling and lack of appetite.
- Nitrite Poisoning
- Almost always occurs while cycling a tank.
- The symptoms are similiar to ammonia poisoning.
- Cyanide Poisoning
- Almost exclusively occurs in fish captured in certain areas of the South Pacific.
- May take a week or two to show up after collection.
- Other than a lack of appetite, there are few symptoms to detect.
- Poisonous Sting
- May be inflicted from a poisonous fish(i.e. Lionfish) or from a poisonous anemone.
- Difficult to diagnose.
- Symptoms include erratic behavior and lack of appetite.
- Other Poisons
- Poisons from the Neutron Bomb Boxfish, Pufferfish or Lionfish which have been released in the tank.
- Anything from cigarette ashes to hair spray can be sources.
- Malnutrition
- Most often occurs when a new fish is introduced into a tank.
- Lack of appetite due to disease.
- First symptom is a sunken belly.
- Oxygen Deprivation
- Normally caused by lack of vertical water movement in a tank.
- Initial sign is fish staying at the surface of the tank water.
- Old Age
- Inevitable.
- Difficult to diagnose.
- Physical Injuries
- Pretty obvious.
- Usually caused by other tank occupants.
- Bacterial Infection
- Symptoms include cloudy eyes, red areas on the body, swollen belly (internal infection).
- Bends (Diver's Disease)
- Rare for the hobbyist to see.
- Normally occurs during collection.
- Other Diseases
- Ick, fungal infection.
