The use of Epsom salts in fish aquariums

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Epsom salts derive their name from the location that one of the first discoveries of the chemical compound took place in, Epsom in Surrey.

As Epsom salts have such a wide range of applications, in health, beauty, pet car and home and garden care, they can be found in a variety of shops, including chemists, supermarkets, garden centres and pet shops. Epsom salts is the common name for the chemical compound magnesium sulphate.


Fish that are fed a diet of fish pellets and flakes can often develop constipation. Signs that a fish is suffering from constipation include bloating and stringy faeces hanging from the underside of the fish. Constipation can affect a fish’s appetite and lead to other conditions such as swim bladder disease. Epsom salts, added to the tank at a rate of between one and three teaspoons for every 23 litres of water, can help to treat constipation due to its muscle relaxant properties.

Buoyancy problems

Fish such as fancy goldfish can develop buoyancy problems as the result of bacterial disease, poor diet, trapped air, injury or poor breeding. Fish with buoyancy problems may either sink more than they should and try to swim upwards or float at the top of the tank, unable to swim any deeper into the tank. Adding one level teaspoon for every 18 litres of water in the tank can help to treat some of the causes of poor buoyancy.


Signs that a fish is suffering from dropsy include a bloated body with scales that stick out in a manner that resembles a pine cone. Dropsy can be the result of a number of causes, including infection, that lead to fluid building up inside the fish’s body. Epsom salts are one of the treatments for dropsy and it is best to treat a fish with the condition in its own tank of other fish are unaffected. Adding up to two and a half teaspoons of Epsom salts for every 45 litres of water in the tank can help to extract the excess fluid from the fish’s body.


Epsom salts can also be used to treat popeye, a condition affecting fish that causes their eyes to bulge out. The eyes are forced to protrude as the result of fluid filling the area at the back of the fish’s eyeball. Along with bulging eyes, other symptoms of popeye include a cloudy white appearance on the surface of the eye. Epsom salts can reduce the swelling in the eye when added to the fish tank at a rate of between one and three teaspoons of Epsom salt for every 23 litres of water in the tank.