Hi I have also had this problem in my tank... Very tough indeed. Although I used Pimafix and melafix in conjunction with each other. I ran two courses. It is safe with corries and fry with low dosage and dosnt harm bio filter or plants...also you need to slow filteration etc. My fish are all extremely healthy now. I now have a new 30 litre fry tank as all my gups and plattys have been thriving and dropping. I think my corries are now mating too. What Im saying is I know these products work without fail. I myself went through mis-diagnoses twice before finding right disease and treatment.
If you are in Australia Pimafix and Melafix should be easy to find. These products treat for fungas and bacteria.
G'Luck
I'm afraid I'm going to have to disagree with you.
Melafix is not meant to stop columnaris - It's a tonic for open wounds and sores, and it's
awfully bad for bettas.
The tea tree oil it's made from coats their gills and makes it very difficult for them to breathe.
Pima fix is not made from tea tree oil, so I don't know much about it.
But no, please no melafix on your bettas. It's just no good for them.