Salt

Salt is a generic name usually referring to sodium chloride, but more broadly any ionic compound, and is essential to life on Earth. Most biological tissues and body fluids contain a varying amount of salts. The concentration of sodium ions in the blood is directly related to the regulation of safe body fluid levels. Propagation of nerve impulses by signal transduction is regulated by sodium ions. (Potassium, a metal closely related to sodium, is also a major component in the same bodily systems). There are many different salts. For more details see salt chemistry on Wikipedia.

Usage in aquaria
Salt is used in the aquarium hobby for several reasons.


 * Adjusting the salinity of water for brackish water or marine animals.
 * Additive in freshwater tanks to aid the occupants due to osmotic pressure.
 * To lessen ammonia or nitrite toxicity (usually in transporting fish).
 * As an aid in treating disease or removing parasites.

It should be noted that the use of domestic 'table salt' is not recommended as this product often has unspecified anti-caking agents and other chemicals, such as iodine, in it. Sodium hexocyanoferrate (E535) is a common agent used to prevent table salt caking and this contains low levels of cyanide. But it is believed to be harmless in the very low levels used in freshwater aquariums for treatment use. Raw sea salt, or kosher salt, is generally acceptable, though always check the products ingredients.

Many freshwater plants do not tolerate any level of salt in the water and will soon perish.


 * Pure freshwater with no salt has a specific gravity of 1.000
 * Brackish water is often quoted as being a specific gravity of around 1.005
 * Sea water has a specific gravity of around 1.020 to 1.024 (3.5% salt)

Using salt
(1 teaspoon = 4.7 grams, 1 tablespoon=14.2 grams)

Marine salt
Salt used for marine aquariums is not plain sodium chloride, but is in fact a complex recipe of many different types of salts. Various commercial mixtures of salt are available, all claiming to be the perfect salt for making up artificial sea water.

Typical commercial mixture for making ~1 litre of sea water:

Then add pure water to make the final weight 1Kg.

This yields sea water of salinity 34.5‰, pH between 7.9 and 8.3.

Salt as a treatment
Salt can be used to kill off Ich, Costiasis, Trichodina and other parasites. There are some studies indicating that the usual 1% solution of salt is becoming ineffective and people are resorting to using levels of up to 3% today.

Salt can be used to render levels of nitrite non-toxic for a limited period of time (3–6 weeks).

Animals that don't like salt
There are several species of freshwater fish that do not tolerate salt in the aquarium and these are listed here. It has been said some may tolerate up to 1ppt of salt for short periods but it will ultimately cause undue stress.
 * Corydoras catfish
 * Plecos
 * Tetras - some species are particularly sensitive
 * Elephant Nose
 * Black Ghost Knife Fish
 * Tiger Barbs
 * Otocinclus
 * Ram Cichlids
 * Wild Discus

Animals that may prefer a level of salt in the water but can live without it

 * Livebearers
 * Indian Glass fish
 * Certain Puffer species

Fish that need a level of salt in the water and can not live without it

 * Marine Fish
 * Brackish Fish

Aquarium Wiki Articles

 * The Salt of the Earth by Robert T. Ricketts

Links

 * The Use of Salt in Aquaculture
 * Salt and Your Pond: Facts, FAQs and Myths (Part One & Two)
 * Salinity - Wikipedia
 * Salt - The Krib
 * Brackish Water - Wikipedia
 * Sea Water - Wikipedia
 * Plants for brackish water
 * Practical Fishkeeping - Frequently asked questions on using Salt
 * AWT Marine Salt Mix Analysis
 * Turquoise Wave - Using Salt to Treat Dropsy