Columnaris , Fin Rot, Tried Everything Nothing Has Worked

I am now totally at a loss as to what to do, I have tried all recommended treatments starting with herbal melafix stuff, then interpet fungus and fin rot treatment nothing worked so after further research suspect columnaris have treated with furan 2 and kanaplex which I ordered from US. Have lost 5 platies, the last 4 are all showing symptoms, I have a dwarf gourami which now has a hole in his dorsal fin, my Angels left fiin is now partially missing, 3 mollies not showing any signs and 3 Corys not showing any signs, help, I really don't want to lose my angel she is beautiful

Tested them all today all as normal, ammonia 0, nitrite 0, nitrate 5, kh 107ppm, gh over 146ppm, I say over 146 cos I'm not 100% how to work it out but it was 9 drops not 8 which is the 146ppm on the api tester.

So it's not the water conditions, it's mainly ammonia and nitrite that cause problems though if the water had been exceptionally hard and alkaline, the softer water fish would have problems.

I have heard about an exceptionally bad strain of columnaris, but that usually wipes out the whole tank in a matter of hours.


I am at a loss to know what to suggest  All I can think of is continuing the antibiotics. I'm sorry I can't be more help