I have a very poorly fish with fin rot. I was wondering if there was a point where you have to 'put the fish down'. My fish has currently lost majority of his tail fin and all of his anal fin. Its starting to affect his side fins too. I have added the recommended dose of fin rot treatment about 2 weeks ago and it seems to be getting worse. How long shall i wait? I dont want my other fish catching this disease. This is the first disease ive had since i first set up so im a little unsure as of what to do.
Cheers.

Not a great situation to find yourself in hey, sorry to hear. hope its not a high value fish, did you find the trigger for the ailment? water conditions/introduced with new fish?

Treatment for fin rot is hard and slow, some species do get some fin growth back very gradually but most will never truly recover from a severe case. what treatment did you buy/use, how long have you been dosing and are you having to dose the whole tank or just a nursing tank?

Did you have carbon in your filter? removed it before dosing?
what species is inflicted?

Has he lost any of the hard rays of his fins or is it restricted to the softer rays in between (the more transparent parts)? What species is it?

He has lost all of his tail fin. Theres just the sticky bits left its also working its way onto his actual tail and also he lost the same amount on his anal fin. Cant get him to eat either. Im having to dose whole tank as dont have a spare for nursing. I used interpet treatment from pets at home. The species is roach.

Have you done any water tests recently? And can you give some more info about the tank? Size, inhabitants etc.? Finrot is often a result of something simple like water conditions so always best to rule out the obvious

I think the answer is in the species. Roach don't make good aquarium fish unless you can provide a very large specialised set up with fast flow, high oxygen etc. What size of tank is he in and how is it set up for filters, power heads etc? Any other tank mates? What temperature? As Suey said, do you have any recent test results for ammonia, nitrite, nitrate and pH?

Also I would switch to a better med such as eSHa 2000 or Myxazin. The Interpet stuff has a reputation for not being very effective.