While both contain the same principle ingredient, there are major differences in the makeup and uses of table salt and aquarium salt.
What is Aquarium Salt?
Aquarium salt is pure sodium chloride or salt and is often produced by evaporating seawater. The pure salt does not change the pH balance of the water or affect the mineral content.
What is Table Salt?
Table salt is principally sodium chloride with the addition of iodine to prevent goiters in humans and calcium silicate to prevent the salt from caking.
Using Aquarium Salt in Salt Water Aquariums
Follow package instructions when starting an aquarium or replacing the water. If topping off the tank to compensate for evaporation use fresh water. If the tank has leaked, replace the water with a salt water mix.
Using Aquarium Salt in a Fresh Water Aquarium
The bacteria associated with diseases of freshwater fish don’t tolerate salt water well. A treatment of 1 tbsp of aquarium salt per 5 gallons of aquarium water can serve as a tonic for the fish. Caution is suggested when adding salt to a freshwater aquarium. Some species of fish, mostly the scaleless species and most freshwater aquatic plants, don’t tolerate salt.
Availability of Aquarium and Table Salt
Table salt is widely available in all grocery stores. Aquarium salt is available at most pet supply outlets.