How to solve a problem like gas embolisms

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Unsightly and agonising, gas bubbles in fish are a horrific infliction - and usually man made! We explain more.

The symptoms of gas bubble disease are obvious. They are small or large pockets of shiny, silvery gas trapped beneath the flesh in some grotesque, glistening lump.

These may be unsightly and look painful, or have more serious health implications. If bubbles start to form inside around the vital organs, such as the brain, liver or heart, then death can be rapid and without warning.

Even outside the fish they can be major health problems. Bubbles around the mouth will hinder feeding, those behind the eye affect vision and bubbles on the body make swimming difficult or painful.

The name 'disease' gives a false connotation that this is in some way a pathogenic condition, but it’s rarely the case. Sometimes, although incredibly unlikely, bacteria may get behind an eye and produce gases as a result of their growth.

Usually the condition is brought about by problems in filtration and circulation. This is more apparent in marine tanks where the density of the water allows for the formation of smaller bubbles than in freshwater — although both types of fish can become sick because of gas embolisms.

Most often, the culprit is an ill-fitting pipe. As water travels through filters, even the tiniest gap or lesion in the hosing can draw in a tiny Venturi of air. This suction of tiny strings of bubbles can start to accumulate in the water until a level of saturation is reached.

These micro-bubbles then enter the fish via the gill, where they start to accumulate in the blood, sticking to each other and forming ever larger bubbles. The process soon accelerates, to devastating effect.

Another, lesser known way for these bubbles to enter fish is through sudden additions of cold water to the tank.

Colder water holds more dissolved gases than tropical water, and, as it warms, these gases will precipitate into tiny bubbles. Just take a cold glass of water to bed one night and look at the formed bubbles in the morning. You’ll see how much there is.

If cold water is added and fish breathe it, the same process will happen inside them. As the fluid warms it releases gas that then forms tiny bubbles inside. The bubbles accumulate and once again we have a problem.

Over time gas bubble disease will cure itself, assuming that the cause of the bubbles is addressed. At the first sign of this problem, check all piping thoroughly and find where the air’s getting in.

Never consider bursting the bubbles. This will harm the affected fish, leave it open to infection, and the stress will often lead to secondary infections. Rectify the cause and leave the fish alone — every time.

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