Ozone doesn't do anything against ich, it does raise ORP, but that isn't a big deal. Most people who use ozone are doing it for the water clarity, when I inject ozone I can get my water so clear it looks like my fish are swimming in air, but thats about all its doing. Are you using an ORP controller? ORP above 500 is going to be bad, so ozone usually isn't recommended for new people, it can be really dangerous for the inhabitants. Good water quality, a stress free environment and good feeding will be the best thing you can do for a tank. Treating for ich will treat the symptoms, but not the cause, ich pops up when things are not good in the fish tank.