Fantail John, forgive me, I couldn't let this pass. While interesting and an alternative point of view, there's too much there that I simply don't agree with.
Salt is commonly used in aquariums by old timers until shops started selling chemicals. It is also much used by Koi (Japanese Carps) breeders. Good Koi is very expensive, so you know they will not put something they don't know well into the water.
Cyprinius carpio is tolerant of brackish water. As such, adding salt at trivially low doses won't do any harm. Whether it does any good is debatable.
You may find some commercial websites "bashing salt". The reason is obvious - if everyone is to use this cheap and readily available salt, then they can't make a profit out of you.
On the contrary. I've written many times about the usefulness of salt under certain circumstances. It's a low toxicity treatment for whitespot, and a good way to shift some external parasites like leeches. But salt is inferior to other medications for treating fungal and bacterial infections, and it has no value at all against things like dropsy.
Salt can kill 77% of all parasites found in water !
So doubtless will cyanide and gamma radiation, but no-one recommends either for general use in aquaria!
Most fish have an internal salt concentration higher than their water environment. Water transfers from higher concentration to lower concentration. (Osmosis) The greater the difference in salt concentration(salinity), the greater the osmosis effect. This difference in salinity causes water to transfer from the water to the body of the fish. Fish have to constantly eliminate the excess water because their body always have more salt than the water around.
When we add salt to the aquarium water, the salinity of aquarium water is increased. Therefore, the difference in salt concentration between the fish and water is reduced. The result is slower water transfer to the fish (lower osmosis pressure). The fish therefore need less effort to get rid of excess water. Therefore the fish saves energy, and the fish has more energy to fight diseases.
Don't even know where to begin here. This is incredibly old school thinking. Fish have mostly evolved for one particular salinity, whether 0 or 35 ppt, depending on whether they're freshwater or saltwater fish. Only some fish, brackish water fish, are adapted to, and appreciate, salinities other than these.
Salt can also help in the production of the fish's protective slime layer and accelerate recovery from wounds. This healing occurs by hyperosmolarity. Fish have a definate specific gravity (concentration of total dissolved solids) in their bodily fluids. If the surrounding water has a higher concentration, the fluids from the wound site goes into the surrounding water, and fresh plasma goes in to replace it, creating more blood flow in that area and making it heal faster. In fact, if you go to a fish shop, you will find that there are many expensive commercial addictives that do the same thing at a much greater cost.
Again, old school thinking. Fish have evolved to have a slime layer of a particular thickness, and making their slime layer thicker than normal isn't going to magically improve things.
This best thing about using salt to kill parasites or promote healing is that it does not damage your biological filter.
Just plain wrong. At the doses needed to treat fungus for example, around 10 ppt, you certainly will stress freshwater filter bacteria. At lower doses, around 2-3 ppt, you can kill velvet and whitespot to be sure, but not fungus and certainly not finrot.
Some fish that do much better with added salt would include Goldfish, Koi, African Cichlids, and livebearers. Indeed, the secret to keeping healthy, robust Mollys, Platys, Swordtails, and Guppys is to add salt.
"African cichlids" covers a lot of ground, and West African and Congo species from soft water habitats don't even like hard water, let alone salty water. When it comes to Rift Valley cichlids, many vets and fish health writers have connected the mistaken use of salt to harden water with something called Malawi Bloat, which is fatal. When keeping Rift Valley cichlids, you should not add salt, at least not by itself. Alongside Epsom salt and baking soda, marine salt mix can be used to make Rift Valley salts. But by itself it is potentially dangerous. As for livebearers, platies and swordtails don't need salt if kept properly, and mollies would do much better given marine salt mix that raises carbonate hardness and pH, rather than ordinary salt.
There are also some fish that do not do well with any salt at all in the water. Some fish that do not do well with added salt includes smooth skinned catfish, Corydoras, Tetras, Angelfish, Discus, Loaches and Bettas. There are others as well.
This is basically everything other than livebearers, so what's the point! Tropical fish that don't come from brackish water conditions should not be exposed to salty water for anything other than short term therapy.
Cheers, Neale
