Salt
is useful in treating and may eliminate parasites that are commonly found on koi. Most fish have an internal salt concentration
of ~1.0%, which is higher than the freshwater environment. By osmosis, water moves from the lower salinity pond water into
the tissue of the fish. In times of stress or kidney infection, the addition of salt can
lower the osmotic pressure, thus reducing the effort of the fish in eliminating excess water.
The conserved energy is then available for metabolic function and the immune system to fight diseases.
Pond
fish actively maintain a natural balance of electrolytes in their body fluids. Electrolytes such as potassium, sodium, chloride,
calcium and magnesium are removed from the water by cells located in the gills. These electrolytes are essential for the uptake
of oxygen and release of carbon dioxide and ammonium across the gill membranes. The lack of electrolytes can cause health
problems in pond fish. During periods of disease and stress, healthy gill function is disturbed. This can lead to the loss
of electrolytes through the gills, affecting the intake of oxygen and the release of carbon dioxide and ammonium from the
gills. Addition of salt may alleviate stress. The addition of salt may also reduce the toxic effect of nitrite, if there is
an imbalance in the biological filtration system.
Salt concentrations between
0.3% to 0.5% are tolerated by koi and can also upset the osmotic balance of some parasites, leading to parasite death. Salt
is thus a treatment option, depending on the type and strain of parasite to be treated. The prophylactic use of salt has however
resulted in development of resistance in some parasites, such as Costia, where several salt tolerant strains are now prevalent.
It is therefore advisable to use salt as a treatment following a proper diagnosis of the parasite rather than as a general
additive. A salt treatment of 0.1% - 0.3% may also assist in controlling some freshwater
algae.
Use only rock or pool salt, NEVER iodized
salt, when doing a treatment. The recommended dose is between 0.1% (100gram per 100lts) and 0.3% (300grams per 100lts) of
pond water. Higher doses up to 0.9% can be used as short term dips. Once added to a pond, salt does not evaporate and is not
filtered out, so it is important to test the salt concentration in your pond before making any
additions. After a treatment, the salt in the pond can be gradually purged from the system by routine water changes. Many
koi enthusiasts advise adding salt around the perimeter of the pond or as a pre-mixed solution
to avoid overdosing the koi.
My story:
I
have seen fingerlings and large Koi hovering over a pile of salt in my pond. After the 2005-spawning season a large Kohaku
injured itself on a venturi in the main pond. A 10mm sized wound appeared between the lateral line and dorsal fin. Within
5 days the wound was healed completely without any medication being needed.
(Please note
that your koi is a fresh water fish and will come to harm should the salt content of your pond be too high – please
be careful when using salt as a treatment).
Article by
Harry Watson
