Use of Salt in Fresh Water Aquariums

Ask any number of aquarium enthusiasts about the advantages of adding salt to a freshwater aquarium and you are likely to get a number of different responses. Some believe salt should be added to the aquarium water on a regular basis while others feel that adding salt is unnecessary and may lead to unhealthy fish. It is important to understand the basic theories regarding salt in a freshwater aquarium so you can make an informed decision about its use in your own aquarium.

  1. Osmoregulation

    • A fish is constantly taking in water through the process of osmosis, the absorption of pure water into an area containing more dissolved substances such as salt, and excreting it through respiration and urination. Since the water coming into the cells contains less electrolytes (salt, magnesium and calcium) than the water being excreted, these electrolytes need to be replaced at a constant level as well. Fish are able to absorb the salt in their urine before it is excreted as well as through their gills from the surrounding water. In most instances fish are able to accomplish this quite well without any additional additives to their water; however, in times of increased stress, such as transportation or when being introduced to a new environment, their need for these electrolytes increases. In addition water that has not been properly conditioned can also interfere with the process of osmosis and cause fish to become more prone to disease. Therefore, in some situations, the addition of salt may be necessary. Some enthusiasts believe routinely adding salt to the aquarium water will aid osmoregulation, prevent stress and reduce the risk of disease.

    Salt as Medication

    • Adding salt to a freshwater aquarium is a proven way to remove parasites and cure some diseases. Velvet Disease, Ichthyophthirius, Gill Flukes, Costia and Chilodonella can all be successfully treated by adding salt to the aquarium. For treatment of the entire tank add 1 tablespoon of aquarium salt for every 5 gallons of water and increase the water temperature to 80 degrees. Perform a weekly water change and add only enough salt necessary for the amount of water being replaced. After three weeks, discontinue adding additional the salt and decrease the water temperature back to normal levels (72 to 75 degrees).

    General Tonic

    • If you choose to add salt to your freshwater aquarium as a general tonic, it is best to use salt specifically designed for aquarium use. This type of salt does not contain additional additives. Begin by adding a teaspoon of salt per week until you have reached a total salt level of 1 teaspoon per 10 gallons of water. For example, if you have a 30 gallon aquarium add 1 teaspoon per week for three weeks. This will enable your fish to become acclimated to the change and enable you to determine if any of your fish show an intolerance to the salt. Since salt does not evaporate from the aquarium, no additional salt is needed except if you perform any water change. Only add the amount of salt necessary for the amount of new water you are adding.

    Caution

    • Some fish such as plecostomus and catfish have a very low tolerance to salt. If these fish are present in the aquarium you're adding salt to, it is important to carefully watch these fish for any signs of distress. In addition, many species of live aquarium plants are intolerant to salt as well.