The Red Sea unit sold in the States has a small cartidge that you fill with dessicant beads (silica gel beads I believe). The air flows through the air dryer and then the ozonizer. Ozone is not very effectively produced unless the air is dry. The beads change color when they absorb moisture. They can then be recharged by heating in the oven.
I have added a canister of Kent "phosphate sponge" (some ceramic granules that also act as a dessicant) to the airline before the silica gel beads. It absorbs moisture very well and can also be recharged in the oven. By having the beads after the Kent "sponge" I can still watch for a color change to know when to recharge, but I don't have to recharge nearly as often.
Allen