I wake up when called . . .@dheltzel
raise the tank temperature to 78-80°F for about 3-4 days I know you cant kill it onthe fish you have to kill lifecycle in the tank.... Dennis I tagged is true Aquarium Master hope he can explain it to you and let you know what you can try!
And you do realize CH that your oscar will eat all your other fish right? only thing that can grow with them is a pleco that I am aware of and they will need a huge tank in short order. Oscars are not the best fish for your tank.
Ich is really pretty simple to treat. Raise the temp as high as your fish can stand without stressing them, stress is the #1 factor in making fish susceptible to disease. Oscars and other fish from the Amazon can tolerate 80 or even 85 without trouble as long as not overcrowded. Add an airstone or powerhead to increase oxygen when the temps are up. The high heat increases the metabolism of the parasite that causes ich and weakens it.
Then, add salt, common table salt, the cheaper the better. Don't worry about iodine, that's harmless, but the stuff they add to make it free flowing in the more expensive brands is not helpful. Start with a teaspoon per gallon. Every day, add another teaspoon per gallon. Watch for any signs of respiratory distress. If they are breathing heavy, so a large water change.
Now, for the real secret -- the white dots are cysts that will drop off and fall to the bottom (or get picked up by the filter). They incubate for a short time, then each hatches into hundreds of little parasites, all seeking a host. If you gravel vac thoroughly at least once a day, you will remove massive numbers of these cysts before they hatch. Remember to add salt to the water you use to replace it.
The salty water really stresses the parasites, already weakened by the high temps. The water changes remove lots of cysts and the also de-stress the fish so their immune systems can kick in and fight off the parasite. I believe most ich outbreaks are not caused by introducing the parasite, it was already there, but a new fish changes the social dynamic and adds stress so at least one fish becomes susceptible and that starts the massive buildup of the parasites that soon overwhelms the defenses of all the fish, making it seem like the new fish brought it. It might have been "patient #1", but might have been infected by parasites already in the tank (or in the pet shop tank, those places are "rife with strife").
I avoid buying pet shop fish as much as possible, and expect any I do get to become sick. So a quarantine tank is a must, preferably setup like I described from combating ich, as this also treats a lot of other problems as well. Once the new fish is recovered and free of problems for a month of so, only then can it go into the tank with others.
I have kept and bred thousands of tropical fish, dozens of varieties, and I have become highly opinionated about the industry and the way fish should be kept. I regularly violated all the "rules" and had fish breed like crazy when overfeeding and under filtering, because I made sure the tanks were a natural as possible, while meeting the needs of the fish I was keeping. Keeping a tank of fish healthy and multiplying is easy if you use the right fish and the right plants and take basic care to keep the environment healthy. Frankly, it got boring, that's why I moved on to poultry . . .