Signs of Tropical Fish Dying Due to Lack of Oxygen

Lack of oxygen in a tropical fish tank, also known as hypoxia, is caused by insufficient maintenance, poor water quality or inadequate filtration. A clean, well-maintained aquarium should never be short of oxygen. When oxygen becomes low, fish show signs of distress, gasp for air and quickly die. Spot the early warning signs of low oxygen in your tank to prevent fish loss.

  1. Fish Behavior

    • If your aquarium has insufficient oxygen, fish hang at the water's surface and gasp for air. Take immediate action to prevent fish loss. In a tank where the water looks clean, it may be an indicator of an underlying problem with the water chemistry or filter. Change half of the tank water and add an aquarium oxygenating tablet for a quick oxygen boost.

    Water Quality

    • Fish breathe through gills and use the oxygen in their tank water to survive. If your aquarium is dirty, fish are unable to breathe properly and dirt particles travel into their gills with the water causing additional stress. Bacteria, algae and other micro-organisms use up oxygen in your tank water, but in a healthy tank there should never be enough to cause problems. If you do not keep your tank clean, these organisms flourish into a slimy floating layer of debris that smothers the tank. Suspended green particles and sludge devour the remaining oxygen, leaving none for your fish.

    Equipment Malfunction

    • Regularly check your tank equipment is in good working order. It isn't always easy to spot a broken filter and it only takes a couple of days without proper filtration for a tank to start losing oxygen and kill your fish. An aquarium filter disperses oxygen evenly throughout the water and good bacteria colonizing the filter media maintain healthy water chemistry. If the filter breaks down, the biological balance is disturbed and water quality deteriorates rapidly.

    Remedies

    • Change some of the water in your tank as soon as you see a fish gasping for air. If one fish starts to look oxygen-deprived, others will follow. If your tank is dirty due to lack of maintenance, set up a holding tank with clean, dechlorinated water and place your fish in there while you clean the main aquarium and restore it to a healthy environment. Regular maintenance and partial water changes keep oxygen levels at an acceptable level.