the pictures shows it is indeed a HITH. medication usually
take 10 days per session. pristine water is the most effective
ways to combate any illnesses. once the cotton like edges of the
HITH disappear, it is a sign of healing off. if the oscar is all
alone in the tank, i would let the medicine remove by regular water
change.
salt do helps in medication by enhancing the oxygenation and softening
the water, but too much of it will not make any good in fishkeeping.
As a side note. This is my second Oscar, and the first Oscar I had I kept in a ten gallon tank for 4 years and only did water changes once a month and he lived that long, crazy huh? It was my first Oscar and I didnt know anything about them.
how big did it grow? what happen? do you think the fish become happy?
oscar in a small tank is like a person in a prison cell. i hope you won't
let your present fish experience the same.