Several people have emailed and asked for an explanation of why ordinary salt is useful in treating fish with Signs of Stress and Disease. Here are a few more facts about adding Aquarium Salt to the water in aquariums.

We are talking here about Sodium Chloride with symbol NaCl, which is the main chemical in table salt. Table salt also usually contains small amounts iodine and calcium silicate. The iodine prevents goiter in humans that eat the table salt, and the calcium silicate prevents the table salt from caking.

Some people have added table salt to their aquarium water and had no problems. But other people have had trouble after putting table salt in their aquarium water. Therefore it is usually recommended that table salt NOT be added to aquarium water.

Aquarium Salt has no additives such as iodine or calcium silicate. Small one-pound boxes of Aquarium Salt, like the one shown at the top of this page, are sold in most places that sell freshwater fish. A one-pound box of Aquarium Salt is very inexpensive.

Salt, NaCl, does not change the pH of water. It also does not change the hardness.

A few fish do not tolerate aquarium salt. Corydoras catfish and many live aquatic plants do not do well with salt in their water.
 
In my aquariums both Corydoras and many plants will tolerate 1 Tablespoon of Aquarium Salt per each 5 gallons of aquarium water, and they do poorly with 2 Tablespoons of Aquarium Salt per 5 gallons.

Salt lessens the number of pathogens in the water. For example very few, perhaps only one or two groups, of freshwater bacteria tolerate aquarium salt well. My experience is that salt is slightly effective in preventing fish trouble in freshwater aquariums but only slightly.

Salt is most effective, when the concentration of salt changes. So I keep my freshwater fish in water with very little salt. If I see one or more of the Signs of Stress or Disease, such as clamped fins, I immediately do all six steps of the Recommended Treatment, which includes adding 1 Tablespoon of Aquarium Salt per each 5 gallons of aquarium water.
 
Click here to read more about the Signs of Stress and Disease, and click here to read about all six steps of the Recommended Treatment.

Marine Aquarists often give their marine fish a freshwater bath, and this is the same principle of changing the concentration of salt, but in this case by lowering rather than increasing the concentration of salt.