Aquarium salt and plants. - The Planted Tank Forum

Salt can be extremely harmful to other fish and can easily kill aquarium plants
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Some invertebrates (like snails) and plants are very sensitive to salt. And if your aquarium uses zeolite to cut down on ammonia, effects may be reversed during a salt treatment. Always remove sensitive invertebrates and zeolite before adding any type of salt.
I wonder if it's the difference between regular aquarium salt and reef salt? Maybe the reef salt has more nutrients the plants need.
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As a general rule of thumb start with 1 tablespoon per 5-7 gallons of aquarium water. This is a safe dose for all fish and plants including salt sensitive corydoras. Some betta keepers only use aquarium salt as a general tonic or preventative. Others use it at higher concentrations to treat for existing parasites, but remember it is not a cure all and can be combined with other things like methylene blue or antibiotics outside of the aquarium in a fish bath to treat stubborn or difficult pathogens. If treating an existing problem the use of high concentration via fish bath should only be done outside the aquarium in a container and last only minutes. You may have read that aquarium salt will cause issues with kidney and liver. This is only true if used at a high level for a prolonged period of time which is never recommended. plants and aquarium salt suggestions
Photo provided by Flickr[Wet Thumb Forum]-Livebearers, Plants, and Aquarium Salt
Photo provided by FlickrCreates ideal environment for livebearers and brackish fish; Safe for plants; Effective alternative to the sodium chloride based aquarium salts so prevalent.
Photo provided by Flickr

Rock salt, or aquarium salt, or sea salt are used by several aquarist to reduce attacks from parasites like ich, costia, anchor worms, skin flukes; or for the purpose of osmo-regulation which in turn helps an injured fish to recover from scale loss or injuries; or for enhancement of slime coat of the fishes as cure/prevention of ailments. I am not well versed enough in fish pathology to make comments about the efficacy of these treatments and I shall not comment about it. I am only concerned as a gardener of aquarium plants how such salt affect the plants.
I have come across the comments of several aquarists saying that they just cannot grow even the easiest of aquarium plant. When I read such comments it comes into my mind that ‘1 teaspoon per 10 gallon’ salt addition advice. Salt does not evaporate from the aquarium once it is added. More salt with water changes and topping up, if unregulated will simply increase the salt content to a level where it shall make it hard for freshwater plants to survive.Freshwater, as in rivers and lakes, does not have appreciable salt content in nature. Most of the plants that we see in an aquarium come from such habitats. As these plants have evolved in freshwater, appreciable amount of salt and/or salty water must be a foreign condition to which a plant has to adapt if it can. Let us examine what salt would cause. Much has been written about the pro's and con's of adding salt to an aquarium. Some support its use unequivocally, while others condemn it outright. As usual, the truth lies somewhere in the middle.

Why would we want to add salt in the first place? After al, there are a few fish that do not do well with any salt at all in the water. Some fish that do not do well with added salt would include smooth skinned catfish, Corydoras, Tetras, Angelfish, Discus, Loaches and Bettas. There are others as well. High concentrations of salt also are detrimental to planted aquariums.

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. Many Ichthyologists consider Mollys and Platys to be saltwater fish that have been adapted to freshwater, and not the other way around. Almost all health problems with Mollys disappear when salt is added. Mollys can actually thrive and reproduce readily in straight seawater. Some saltwater aquarists use Mollys as "cycle" fish in their saltwater aquariums. The usual recommended dose is 1 tablespoon of aquarium salt per 5 gallons of water. This does does not seem to harm most plants, but higher doses may.

Some people keep mixed community aquariums to include both Mollys and Tetras, Platys and Corys. I have kept these fish in water with added salt for years, and have never noticed any particular problems to the Corys or Tetras, although they will not readily breed in water with any salt added. Corys and Tetras can best be bred in soft, slightly acid salt-free water, so that may be a factor for you if you wish to keep these particular species for breeding purposes. You may not want to keep Corys and Tetras intended to be bred in community tanks with added salt.

Advantages of added salt include better osmosis balance for the fish (who must maintain a proper internal/external balance of water). Salt also reduces or eliminates nitrite toxicity. In a cycling tank, nitrites can be quite toxic, but not with added salt. Indeed, marine fish are completely free of worries from nitrite toxicity due to the high salt content of seawater. Experiments with nitrite levels as high as 25 ppm cause no problems for saltwater fish. A similar effect can be expected with freshwater fish, although of course we will not be adding salt at the same rate as for saltwater fish. Salt also reduces parasite infestations, since salt interferes with the life cycle of many (or most) external parasites.