buonasera, Lorenzo
I do understand that many hobbyists are concerned about ozone use.
But rest assured that it is the standard for professional aquarists in coral farms, fisheries, public aquariums, etc.
It is true that ozone weakens some plastics and rubber, but it takes many many years for the damage to have any small impact.
And this only relates to the skimmer or cylinder that you inject into because all outflowing water must be passed over carbon.
Therefore... all other plastic, rubbers and your silicone seals are never put at risk. In fact... if there were enough residual ozone getting past the ozone reaction chamber... your fish would be dead long before any seals were ruined
Please... have no fear. Ozone is easy and safe to apply if done correctly. Just like using iodine or calcium hydroxide... both of which can be quickly lethal to aquatic life if they are overdosed the same.
As for what size ozone and dosage... please follow the mfg recommendations for tank size, and be sure to only ever dose ozone via a RedOx controller. This makes it safe and easy. Dial your setpoint on the controller to 350-400mv
kind regards,
Anthony