Actually you don't need medication for fin rot and Furan-2 will do nothing for it honestly. What you need to do is start doing daily water changes with water conditioner of course, with a container that small you should be doing daily water changes anyway.
If you want to save you some troubles, you should invest in something that is at least 1 gallon if not 3, that means less ammonia will build up to poison your fish. Ammonia can build up very quickly, a matter of sometimes one a few day's and in a container that small, it will take maybe a day to get to poisonous levels.
If you want to save you some troubles, you should invest in something that is at least 1 gallon if not 3, that means less ammonia will build up to poison your fish. Ammonia can build up very quickly, a matter of sometimes one a few day's and in a container that small, it will take maybe a day to get to poisonous levels.
And then, if you can, start doing daily 100% water changes which involves you taking him out in a cup that's never seen soap and then dumping all his old water, getting new water and making sure it's around the same temp;26 C. And then acclimate him to the new water after you've put your water conditioner in.
