Okay. Do this:
1) Do roughly 20% water change
2) Add 3 teaspoons of salt per gallon. If you already have salt added, then replace the salt depending on how many gallons you took out. Example is you took out 2 gallons of water so you add 6 teaspoons of salt.
3) Boost the temperature to around 85-87F. You don't have to worry about oxygen levels. Salt promotes gill function so the little bit of lower oxygen won't make a difference.
4) Wait it out for about 3-4 days
5) Lower the temperature to about 81-82F.
Ich free tank!