Adding Salt in aquarium water
Table salt, or common salt has a scientific name Sodium Chloride (NaCL).
It is a natural compound widely and abundantly distributed in nature,
making up nearly 80% of the dissolved material in seawater.
If you see a bottle of water conditioner in the shop, look at the label
saying what it contains.
If the main ingredient is NaCL, then you'll better save your money and
buy salt in the supermarket instead.
Also, some shops sells sea salt mix which is for marine tanks, those
will increase hardness, pH
and other parameters that really don't need to be changed. In short
just use normal salt.
If possible, try to find salt with no addictives added, in the supermarket
and NOT in hardware shops. Even if it has addictives, I do not
think the addictives are dangerous otherwise there will be a warning
against consumption by people. You may think that we humans are bigger
than fish and so it will not affect us. However, humans also consume
salt daily and any toxicity can build up in our liver. If addictives
in salt are dangerous, then I am pretty sure it will not be approved
for sale in the supermarket as fit for human consumption.
No Yellow Prussiate of Soda (YPS) should be in the salt. It is hazardous
to fish because it dissociates into Prussic Acid in water. If you have
followed the 'no-addictives' rule, then your salt wouldn't have YPS
either. Just included as a FYI only.
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.
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.
Salt can kill 77% of all parasites found in water !
Adding Salt in aquarium water
How Salt benefits fish health
Most fish have an internal salt concentration higher than their water
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
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
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.
This best thing about using salt to kill parasites or promote healing
is that it does not damage your biological filter.
Beneficial bacteria in a cycled tank converts ammonia produced by fish
into nitrates which are absorbed by plants. These "good bacteria"
only build up over a period of time in an established tank. However,
most commercial medication can wipe them out once added to the water,
causing water conditions to worsen at the worst possible time (when
your fish is sick). And if your fish pulls through, you need to remove
the medication from the water before your tank can re-cycle and grow
new beneficial bacteria.
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.
NOTE: Salt does not evaporate into the air. Therefore, if you
are only topping up
the water level in your aquarium, you do not need to put in more salt.
If you do, the concentration of salt in your tank accumulates more and
It is recommended to use one teaspoon of salt per gallon although
a little more will probably not harm the fish.
Caution: Too much salt is not good.
If you add too much salt to the water, the reverse osmosis happens.
As we learned, water transfers from high to low salt concentrations.
If the water surrounding the fish has too high salt, water transfers
OUT of fish,
and your fish will die because of dehydration (no water in fish).
In fact, this is the way some water parasites are killed. Their body
have a much lower salt concentration than fish, just slightly higher
than the water they are in.
So if you add a little salt to the water, it reduces the osmotic pressure
for the fish,
but reverses the osmotic pressure for these parasites, killing them
while benefiting the fish.
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.
Salt Concentration 0.3%-0.5% (3-5ppt)
- upsets the osmotic balance of some parasites, killing them.
- detoxifies nitrate
- controls some forms of algae (ie string algae)
0.3% equals 3 pounds of salt in 100 gallons of water.
There are commercial testing equipment specially designed to test salt
However, unless you are a commercial fish breeder it is usually not
cost-effective to buy one.
Just use salt in moderation, at about one teaspoon of salt per gallon.
(Although anything below three teaspoons will probably not be harmful
Feedback from visitors
I have received some queries about table salt and my answers are as
Question: Table salt contains iodine addictive which can be harmful
Iodine is required for vertebrates (Iodine is a halogen). "Iodine
is necessary for metabolism as an essential part of thyroid hormone,
which is our metabolic pacemaker" -quote from a doctor friend.
An iodine deficiency can cause goiter in humans, which is why some table
salt contains added iodine, as a way to benefit everyone (since everyone
consumes salt). In fact, a number of fish can also develop goiter in
captivity if iodine is deficient.
The concentration of iodine added in table salt is extremely small
(since there are many people who consumes a lot of salt in their food.
To reach toxic levels of iodine, you need such a high concentration
of salt that your fish will be killed, dehydrated and pickled by the
extreme salt content before iodine can reach levels high enough to harm
it. In fact, the minute amount of iodine that ends up in the aquarium
or pond is likely beneficial as a potential source of essential iodine
for both plants and animals. The myth that says iodine in salt harms
fish is without foundation.
Question: When sunlight shine on your tank, will salt will react into
No. If so, then we would have be warned against eating fish&chips
outdoors and most open air eaterys would have been shut down. Also,
salted fish and salted vegetables (popular in asian markets) would have
killed more people than fish.