The Use of Epsom Salts in Fish Aquariums

Epsom salt is the common name for the compound magnesium sulphate -- a chemical containing magnesium, sulfate and oxygen. Despite its name, Epsom salt doesn't contain sodium. Magnesium is a mineral that is important for many systems of the human body -- especially the nerves and muscles. It's also beneficial to aquarium fish suffering from maladies such as dropsy, constipation and swim bladder disorder. Epsom salt may be added to fresh water fish tanks to alter the chemistry of the water.

  1. Increasing Water Hardness

    • Epsom salt may be used to increase water hardness in freshwater aquariums. Harder water contains more-dissolved magnesium and calcium. Some species of fish require hard water while others require soft. The degree of hardness impacts the tank's pH. Harder water is more alkaline -- soft water is more acidic. Water hardness is expressed in the amount of calcium carbonate (CaCO3) it contains. According to Aquatic Community, "adding 1 milliliter of it [epsom salt] per 10 liters of water will increase the permanent hardness by roughly 70 mg/L CaCO3." Determine the optimum pH and water hardness levels for the type of fish in your aquarium before altering the tank's chemistry. Any major shift in pH levels can stress, even kill, fish. Avoid a change in pH greater than 0.3 in a 24-hour period.

    Epsom Salt for Constipation in Bettas

    • Constipation is a common condition suffered by many types of fish, including Betta. Symptoms include belly bloat and loss of appetite. Constipation is usually caused by overfeeding or feeding a low-fiber diet. Stop feeding a fish with this condition for 24 to 48 hours. If you don't see improvement, offer the fish tiny pieces of the inside of one fresh pea (canned peas are too salty). If the fish shows no improvement, consider giving it an Epsom salt bath, which acts as a muscle relaxant. Watershed Aquaculture suggests pouring half of the tank's water into a clean container. Add 1 tbsp. of Epsom salt for every 1 gallon of water. Have the fish swim in the solution for 15 to 30 minutes. Remove the fish promptly and return it to its aquarium if it appears stressed or relieves itself.

    Epsom Salt for Treating Dropsy

    • Dropsy is a potentially fatal condition in which the kidneys of a fish fail, leading to fluid retention. A fish experiencing dropsy has a bloated abdomen and raised scales. According to Dr. Barbara Scott, Epsom salt may be used as part of dropsy treatment. She suggests isolating the sick fish in a separate "hospital" tank, then adding Epsom salt at a rate of 1/8 tsp. for every 5 gallons of water. The Epsom salt will relieve swelling. She also suggests feeding the fish a special diet containing antibiotics. Never use aquarium salt, or any other type of sodium, to treat a fish with dropsy; it may worsen the condition.

    Epsom Salt for Swim Bladder Disorder in Goldfish

    • Swim bladder disorder can strike all freshwater fish -- especially goldfish. Fish with this condition have difficulty swimming upright because the swim bladder, which is normally filled with air, is compromised. Swim bladder disorder is caused by gulping too much air, impacted eggs, disease or constipation. According to Desktop Goldfish, treatment includes skipping feedings for two to three days, then feeding a de-skinned pea. If that doesn't help, Desktop Goldfish suggests increasing the tank water temperature to 78 degrees to 80 degrees Fahrenheit and adding Epsom salt at a rate of 1/8 tsp. per 5 gallons of tank water.