hi,
i cured my fish. i put him for a day on metronidazole i.v. then i changed 60% water and loaded with probiotic bacteria sachets{ lacto bacillus and other spores which are given to children with dysentry}. the theory is when i cleaned my tank i used potassium permanganate to oxidise all the wastes as i found my fish rubbing the substrate. but i foolishly left the filter pump inseide the tank. so i killed all the beneficial bacteria. due to this it got stressed and got some bacterial stomach infection.
so i followed the above steps. even if we use metronidazole. it kills all the beneficial bacteria also. so this interrupts the digestive process. to kick start this i used this probiotics.