Basics
If the disease cause is not obvious, check water conditions, including temperature, pH, GH, KH, NH3, NH4, PO4, NO2. Observe the fish for symptoms. Check any recent changes.
Hospital Tank
Diseased fish should be isolated whenever possible so they are not likely to spread infections among other healthy fish in the tank. The best way to isolate sick fish is to set up a hospital tank. If possible move all sick fish to a hospital tank, without sand, live plants and decorations. If the treatment is an antibiotic antiseptic or copper based, remember to remove all carbon from the filtration system. Make sure the biological filtration in your aquarium which cycle harmfull ammonia and nitrites is not destroyed by drugs. The tank should be furnished with a reliable heater that will not permit much temperature variance. The tank should be furnished with an air stone. After treating the sick fish, disinfect the tank.
Baths
An alternative means of treating a fish is to give it a short bath in a bucket containing water and a medication or salt.
Salt bath
A salt bath is a good way of treating the fish without damaging the beneficial bacteria. It is a good antiseptic and fungicide. Most table salts may contain additives like magnesium sulfate to keep them from clumping and appear whiter, which might not be beneficial to fish. Aquarium salt is recommended, although Kosher salt or rock salt is satisfactory.
Heat Therapy
Heat therapy of raising the water temperature, can be administered to kill certain parasites. The temperature should be raised gradually. Sometimes diseased fish cannot handle such a temperature change, or the species can not tolerate high temperatures. Discontinue treatment if any side effects occur. Aeration is necessary since less oxygen is dissolved in warm water.
Medications
Commercial fish medications are not regulated by any government agency. This means that some commercial medications have not been tested for safety or effectiveness. Thus some medications may be completely useless and may be even harmful to aquarium inhabitants.
Treatment Options
* Conservative treatment
o Temperature modifications
o Changing water conditions
* Pharmaceuticals
o Drug baths
o Topical drugs
o Feeding drugs
o Injecting drugs
* Surgery
* Killing the fish
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as I am sure you already know Columnaris is a bacterial infection
