Flexibacter columnaris

the most commonly seen pathogen in aquariums is Flexibacter columnaris which is often mistaken for fungus, as most of us are taught that white fuzzy growth on the skin of a fish means fungus.

however, white or grayish white, fuzzy looking lesions that occur on normal skin, mouth or fins are much more likely due to columnaris. true fungus generally grows on infected wounds or torn fins .. in other words, it grows on dead tissue.

symptoms of this disease include grayish-white spots on some part of the head, fins, gills, or body usually surrounded by an area with a reddish tinge. the columnaris lesions on different species of fish vary in size, location, and appearance. these may appear thread-like, particularly around the mouth, giving rise to the incorrect name of 'mouth fungus'. characteristic lesions can appear on the back, the fins, gills and belly. catfish, in particular, tend to have lesions on their bellies and sides. fins will deteriorate and sores may appear on the body. the gills may be affected, giving rise to bacterial gill disease. It may cause 'shimmying' behaviour in fishes, particularly livebearers. Mollies, for some reason, seem to be particularly susceptable. although columnaris most commonly involves external infections it can occur as an internal systemic infection with no visible external signs.

Columnaris is opportunistic and strikes when a fish is stressed. Poor water quality, sudden changes in conditions, wide temperature swings, high nitrate concentrations, low dissolved oxygen concentration, crowding, shipping, and bullying can also trigger columnaris.

Columnaris is more virulent at temperatures above 77 degrees. summertime is "prime time" for this disease and fish almost always suffer significant losses when shipped in warmer weather. hard water with a high Ph seems to accelerate the course. under appropriate conditions columnaris can spread rapidly and cause catastrophic losses. one strain has a virulence that is low and it takes a few days to kill the fish. a highly virulent strain will kill a fish in under 24 hours.

If your fish has the highly virulent strain, there is not much that you can do to stop it or treat it. fish often die so quickly that there may not even be enough time for them to show any external signs of infection.

Treatment: First, slowly lower the temperature in the tank to 75°F to slow the course of the disease. also, since columnaris thrives in low oxygen conditions, the addition of an airstone or lowering the water level to create more splash from the filter will also help.

the most effective treatment for columnaris if the fish is still eating is medicated food containing oxytetracycline. Aquatronics makes such a food, as does Zeigler.

often however, the fish is not eating by the time symptoms are noticed. Antibiotics in the water would be the next treatment option. Erythromycin (Maracyn), nitrofurazone, nifurpirinol, acriflavine, chloramphenicol or tetracycline can be used to treat the columnaris itself. however, a fish infected with columnaris often falls prey to a secondary infection which is resistant to both of these. therefore, a combination of Maracyn and Maracyn Two or tetracycline and kanamycin is recommended. CONTINUE TREATMENT FOR A MINIMUM OF 10 DAYS.

This is one nasty disease! But I would also encourage to you to address the other issues as well. The ammonia levels could also be a leading cause of death.

If this is the disease in your tank, that's good news in the sense that you have ID'd it and can now treat for it!!!

Here is your initial post (w/ some updated posts) http://www.aquariacentral.com/forums/showthread.php?t=104626

I REALLY hope this works out for you!!

You need to give water perams.The bottom of your tank is probably a toxic dump .Too much fish poo and uneaten food leading to disease..This will show up in a high test nitrate reading in a cycled tank(above 20).You could try changing 30% of the water with a gravel vac every day .See what happens with your 4 remaining fish in the next 4-7 days before adding more or starting over.

With all of the infections I would dry out your tank completely for 3 days, maybe hit it with some bleach to be sure (1:10 ratio)

Regardless, I would urge you to strongly consider a fishless-cycle to get your tank started. Obviously it doesn't harm any fish, and there is no stress during during the process

Here is a guide on picking the correct Ammonia source - http://www.aquariacentral.com/forums/showthread.php?t=88486

Here is an article on cycliing w/out fish: http://www.aquamaniacs.net/forum/cms_view_article.php?aid=31

Columnaris barcteria is always present in aquariums, so you can start all over from scratch if it makes you feel better, but probably isn't necessary. The disease only attacks fish that are stressed and weakened in some way. Keep your water clean and your parameters good and the disease will have nothing to feed on and return to dormant levels.

I would just do a 50-60% water change, and let your cycle continue, rather than start all over and waste all that time. COlumnaris thrives best in warm water and low oxygen levels, so you could lower the temp to around 75 and add an airstone during the rest of your fishless cycle. Once it's time to add fish again, your water parameters will be perfect, and you are going to be fine.

http://www.aquatic-hobbyist.com/profiles/disease/freshwater/columnaris.html