Columnaris: Prevention and Cure Guide

Columnaris is a bacterial infection that affects aquatic fish species but is often mistaken to be a fungal infection owing to the mold-like lesions that it exhibits on affected fish. The disease is quite common in live-bearing and catfish. The bacterium that causes the disease has got a rather columnar shape hence its name columnaris. It is unfortunate but true that the bacterium that causes the disease is usually present in almost all aquatic atmospheres.

It is a highly contagious disease that may easily be spread via things like specimen containers used in tanks, nets, and other related items. This is why it is best to use sterilized items in aquatic settings especially when you got multiple tanks that used shared items.

What causes the disease?


The disease is usually caused by a host of factors some of which may easily be avoided by simply following the laid down procedures of ensuring aquarium hygiene. Below are some notable causes of the disease in aquarium fish:

Aquarium environment

The Columnaris bacteria have been found to mostly affect fish that have been stressed by poor water conditions. Remember in the wild, most of the bacterium present there exists in very low concentrations. In an aquarium setting though and especially when the water conditions are not well taken care of, the concentrations can really shoot up. The conditions can get even worse when there is overstocking of fish in the tank. Lack of filtration and failure to do water changes as per the laid down requirements can really add much salt to the injury.

Insufficient diet

Fish that are poorly fed can really suffer stress and also suffer from poor immunity such that they will not have much chance against these bacteria.

Composition of the water

There are certain kinds of fish that in the wild usually live in waters that are almost free of bacteria due to the fact the pH of such waters are usually very low. When such kinds of fish are for instance then captured and then kept in aquaria of high pH, they stand a chance to suffer from this disease.

Columnaris symptoms

A large percentage of Columnaris infections are usually external and will manifest as white or grayish to white spots on the head and areas that surround gills or fins. Lesions will later occur and will become visibly clear when the condition is already deteriorating.

As the infection continue to advance the affected area may show yellowish or a somewhat brownish color with the surrounding areas appearing tinged red in color.

There are also other signs where the affected fish will be seen to be isolating itself from the pack and even in some cases trying to go above the water surface gasping for air. You can also see the fish appearing pale with some sort of ‘bloating’ around the pectoral or the ventral fin areas. In more severe cases the fish may simply just drop to the bottom of the tank appearing weak and out of energy to swim. In this stage if immediate response is not taken the fish will be gone in just a few hours.

The reason why you may see the fish trying to get to the surface of the tank gasping for air is due to the fact that the bacteria usually attacks the gills. The bacterium has the tendency of easily finding its way into the bloodstream. Unfortunately, once it gets into the bloodstream, the death of the fish will really follow very fast and at this juncture sadly there is nothing that can be done to salvage the situation.


Just like the old adage goes, ‘prevention is usually better than cure’ and this is why all new fish before being introduced into the common tank need to be quarantined. Putting new fish in a tank of their own before introducing them into the common tank for some few weeks can show you those signs. If you notice this better institute proper treatment to the fish and then make a close observation of them to see if the disease has gone away completely before introducing them into the common tank.

Another great way to prevent this disease from taking a toll on your stock for aquarium fish it to always maintain high standards of hygiene. Always clean the tank of any food leftovers and also install better filters to help recycle the water. Perform regular water change to make the water fresh and ensure to check the parameters of the water by checking the pH and also the hardness.

Always ensure that the temperature in the tank is set to the recommended standards for the fish being kept in the tank. This will go a long way in ensuring that the fish live a healthy life devoid of stress.

You can also prevent the disease by ensuring that the population of the fish within a given aquarium is reduced to the recommended number as per the amount of water in it.

You can as well use non-chemical sterilizers to help keep the aquarium water at a minimum thus helping keeping the disease in check. UV sterilizer is a good choice of non-chemical sterilizer to use in the aquarium water.


Columnaris treated is not complicated and a good antibiotic treatment plus some little bit of chemicals added in the water should be able to eradicate it. For external treatment of the fish, using Acriflavin, Furan, Terramycin or copper sulfate will do.

Terramycin on its part has been found to be very effective at both external and internal treatment of the disease. For internal treatments, it is best used to treat foods which will be eaten by the fish. You may also add salt to better enhance the performance of the gill but there are certain fish species that are sensitive to salt. In this case, it may be best to avoid using salt and seek the help of experts.

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