Columnaris (flexibacter - gram-negative)) I just pulled a large male Paraneetroplus breidohri from the brink of death.
Start treatment right away by:
1. isolating the fish, making sure to use cooler water (~75F) and increase aeration.
2. Using a combination of Kanamycin (specific to gram-negative), and furazolidone/nitrofurazone (treats gram-positive (secondary infection) and gram-negative as well (Furan-2 from API) added to the water in the recommended dose. Also, even though kanamycin is absorbed through the skin of the fish, once he starts eating, soak some food in kanamycin and get him to ingest it.
3. Don't give up. It may take a week or so for improvement to be noticed (ie may get worse before it gets better).
4. If secondary fungus appears, I use methylene blue and/or pimafix. Also salt (1 tbsp per 5G) is effective against flexibacter too. Your case is going to be severe and if not treated, it's just a matter of time (can be sickeningly quick) before death occurs.
Here's a link that you might want to go to:
http://www.google.ca/url?sa=t&rct=j...=yJTVVHTDj8a7RuqpQR8uYg&bvm=bv.47534661,d.aWc
Good info. Good luck.
Jim