A common problem indicated to us by our customers is fish gasping at the surface of their aquarium or fish bowl. By gasping we mean the fish opening and closing its mouth at the surface. It is gasping because it can’t get enough oxygen and there is more oxygen at the surface, the fish is unable to get sufficient oxygen from the water.

Possible reasons your fish is unable to get sufficient oxygen from the water include:

1. Pollutants - a build up of ammonia, nitrite and chlorine can cause irritation and damage to the gill membranes. The fish then produces additional mucous to protect its skin and gills from irritation making oxygen uptake less efficient. Nitrite will affect the haemoglobin within the blood reducing its capacity to carry oxygen.

2. Physical damage - as a consequence of poor water conditions, bad handling or parasitic attack. Damage reduces the surface area of the gill tissue that can absorb oxygen.

3. Gill Parasites - Gill flukes, protozoans and bacterial infection cause damage to gill tissue and irritation to membranes resulting in excessive mucous production.

4. Blood parasites - High levels of parasites will absorb oxygen before it reaches the vital organs within the body.

5. Low oxygen levels in the water - due to overcrowding in the aquarium or insufficient water movement to allow oxygen enter the water. High levels of plants or algae can also remove oxygen during the night when they are not photosynthesising and producing oxygen.

How do you decide which one of these is actually causing the problem?

A good guide comes from the time of onset of poor health and its rate of spread. There are 3 main possibilities:

1. Affects all the fish, or all the fish of a particular species or size and occurs quickly. This suggests a water quality problem and requires partial water changes or increased water aggitation.

2. A small number of fish are affected initially but this number gradually increases. This suggests an infectious disease and can be treated using a specific treatment recommended to you by Pet Essentials trained staff.

3. Only one or two fish are affected and the problem does not spread to any other fish. This suggests a non-infectious disease, physical injury or malformation.