However do not confuse Columnaris with the spores of Saprolegnia the cotton wool ball with hair like growth structures seen on damaged fish. Without a microscope, Columnaris can look like Saprolegnia and is often treated as fungus, sometimes with poor results.
The best way to tell with the naked eye (using a magnifying glass) is the hair like growth structures of Saprolegnia/Fungus.
WITH a microscope, scrapings from a columnaris lesion then placed under a microscope will reveal long, thin, rod shaped motile bacteria. The bacterial clumps form microscopic columns or dome shaped masses, hence the name columnaris.
Columnaris has similarities to Aeromonas bacterial infections in that both are opportunistic (both generally present in some location of an aquarium), however since Aeromonas is a facultative bacterium & often anaerobic, it is more prevalent in a tank with high amounts of pollution, DOC and especially poor circulation.
While Columnaris being aerobic (preferring high oxygen environments) can occur in tanks with good filtration/circulation, however it is common in a tank with poor Redox/mineralization, overcrowding, high temperatures, and stress (such as an aggressive fish tank where many inhabitants are constantly bullying others).
As well weak genetics from in-bred fish (as with many Guppies and Bettas) or fish such as "feeder" or "carnival" goldfish that are often permanently damaged for early life crowding are also often at risk for Columnaris infections.
Unfortunately the above point is missed by many who often cite dirty, stagnant, or otherwise poor water conditions as cause of Columnaris, but since Columnaris is , it simply thrive in poor water conditions that are low in oxygen as can Aeromonas or Saprolegnia.
This is NOT to say that sudden shifts in parameters such as spikes in ammonia (assuming an aerobic environment), can will not trigger Columnaris, as this too is a stressor that can allow for an opportunistic Columnaris infection.
HOWEVER, as I have noted many times in my years in aquarium maintenance and "sick fish" service calls; dirty, foul, under filtered, low oxygen environments, RARELY trigger Columnaris infections.
Adding aeration without correcting mineralization problems based on false assumptions about Columnaris while ignoring ESSENTIAL mineral ions (Calcium in particular, but sodium chloride too) will only further force an out of balance Redox and not help with a cure of a true Columnaris infection!!
In lieu of often unavailable scientific microscopic identification, the above point is often noteworthy in identifying aerobic Columnaris from often anaerobic Aeromonas or the Mold Saprolegnia (generally referred to as "Fish Fungus").
Please read further for a better understanding of this bacterial disease as well as treatment and prevention (there is also a section about as well)
Parasite Treatment Kills Many Fish at Texas Aquarium - NBC News
Sudden exposure to environmental changes can make fish go ‘loopy’ for a while. Such fish show all the symptoms of swim bladder disease, swimming poorly or at odd angles. Adding very cold water to a tropical aquarium is a classic way to shock aquarium fish. There’s no treatment as such, and if the fish can recover, they will do so given a few hours. Switching the tank lights off for a while often helps, partly by removing one source of stress, but also by encouraging the fish to rest quietly rather than try to swim about.
Water Treatment | Aquarium Basics | Tropical Fish Hobbyist Magazine
The aquarium will need to be kept this way for at least two weeks and ideally three weeks. The aquarium fish won’t mind being in the dark, though you may need to allow light from the room into the aquarium while them. But take care to limit such periods to a few minutes each day. Once the treatment is finished, remove the blanket for the first day, but don’t turn on the aquarium lights, so the aquarium fish aren’t suddenly exposed to bright light. Then turn down the aquarium heater and carry out a series of water changes to reduce the salinity down to normal.
Aquarium Sick Fish Stress & Disease Identification & Treatment ..