PaulB,, when you introduce new fish, especially sickly fish, to your tank they do not have this immunity you speak of. So how exactly do they just get immune when you like to make a point that you hope you have a ton of ich and other disease/parasites in your tank? Immunity happens over night in your tank? No, the ozone kills enough for them to get better and the diet you feed them allows them to get healthy.
Fish from the sea are all immune. Their immunity is in a very weakened state when we get them because they are severely stressed and probably haven't been fed.
When I put them in my tank of course if they are real sick, they die. That rarely happens because my tank is natural and I don't buy a fish I can't properly feed and I never try to get it to eat something it isn't supposed to eat.
In a few days as they are eating the correct food, their immunity starts to work and the fish lives on long enough to get me in trouble because no one believes in immunity so I must be very lucky. Or it's the Ozone. :rolleyes:
People fear Ozone for some reason like it is radioactive fallout. If it is in your home, you would smell it right away and it won't kill you. I don't even use a controller, I don't tweek it, I don't pay any attention to it, it is just there. I like it like so many people like test kits and quarantine tanks. It's just me. I don't feel it does anything to parasites because I am sure if there are ten thousand parasites in my gravel and 6 of them a day swim up to the surface to get caught in my surface skimmer to get Ozonated, those 6 parasites may get killed but their thousands of cousins are happily there trying to infect my immune fish.
To set up an ozonizer, you plug it in and connect an air hose to it, then go out to dinner and forget about it. I never touch it and sometimes I shut it off to clean my skimmer top and forget to turn it back on for a month or two.
I have been told my fish don't get sick because of getting trapped in my UG filter, there is something in my tank that eats parasites, my algae filter scares them away, ozone or my favorite, luck.
My ozonizer cost about a hundred bucks many years ago but most people spend that on test kits, ASW to change water every week, hospital tanks, quarantine tanks LED systems and medications. So to me my ozonizer is cheap. If it croaks I may not even replace it because I am not even sure it does anything.
If people feel the Ozone is the key, it's silly not to use it and much better than the alternative. But it's your tank. :cool: