OZONE
So you have an ozone built into your spa! Good Choice!
Ozone...naturally healthy.

A Spa Ozonator converts oxygen to small safe levels of ozone,(O3 ozone gas), pumping it into the water to sanitise your spa.
Ozone destroys odours, stops eye and nasal irritation and kills bacteria faster than chlorine or bromine, increasing bather protection.Ozone gives your spa clear, sparkling, healthy water which feels absolutely brilliant. Save time and money, an Ozonator has little to no maintenance, giving you more time to sit back and relax.Ozone is the natural choice for spa hygiene and greatly reduces the chemical demand in spa and pool water sanitising.This in turn reduces operation expenses by up to 85%

Yes !......you still need to add chlorine or a chlorine alternative.

An ozone in no way replaces the need for a sanitiser such as chlorine it only helps you use less of it. Ozone in conjuction with Nature2 can eliminate the use of Bromine.
Make Sure your ozone is working correctly on a regular basis! Depending on the type of ozone injection system you have the ozone bubbles will come out of a jet,wall fitting or grill.Usually located at or near the bottom of your spa.Easily identified bubbling should be present with a distinct smell.Or your spa may fitted with an ozone De-Gas/Mixing chamber, which will eliminate the bubbles and the off gas smell and converts the headrest, hardcover damaging ozone off gas, back to safe oxygen and carbon dioxide once it has done its job. Remember if there is no bubbling from the ozone jet the ozone may not be working. Make sure you know which system you have and how to identify if yours is operating correctly.Ozone, unlike Bromine does not last in the water longer than 18 secs, so it needs to be turned on at least 6 to 8 hours a day to be affective.Having the ozone connected so every time your pump switches on, is one way to acheive a good mixing and dosage.Another way which is now commanly used, is a 24hr circulation system. This method uses a small circulation pump costing less than a 75Watt light bulb to run, and it injects active ozone 24hrs a day.

There are two types of ozones1.U.V. lamp ozone.Which is basicly a special type of flurecent light.these units have a blue indicator light so it easy to see when it is on. 2. C.D. (Corona Discharge) ozone.Which is an high voltage electrical charge produced from a transformer into a sealed chamber producing an ozone gas discharge.

How Long Does an Ozone unit last for?
A U.V. type ozone will only last about 2 to 3 years before the percentage of ozone being put out drops down below 20%,even though the blue indicator light may still be on it wont be producing the same level of ozone.The Corona Discharge type will last as long as the volt charge box and components, which means it could last about 5 to 6 years still producing the correct amout of ozone.

NATURE 2
What is Nature 2?
Nature 2 is a Continuos Silver Ion Purifier cartridge.The spa cartriges have silver and zinc coated ceramic beads, where as the swimming pool cartridges have Copper and Silver. The reason for this is that Zinc is a Copper alternative and is better suited to heated water.The coating is released into the spa water when rushing water passes over it. So it needs to be located inside of, or on top of your filter cartridge to work properly. It helps in the fight to control Microbial Contamination.The unique combination of minerals in the Nature 2 purifier helps naturaly kill bacteria for up to 4 months. It is compatible with Chlorine and ozone, but still, even when used with ozone must be used inconjunction with the minimum legal level of sanitiser.

How does it Work?
The flowing water, through a chemical erosion process, carries with it silver and zinc ions adding a sanitizing residual to the spa water. Bromine, sodium bromide and biguanides should not be used with nature 2 because it coats the beads and does not let the silver ions be released. So if you have been previously using those chemicals you will need to clean the shell and the filters and compartment thoroughly before using.The ozone works inconjunction with nature 2, it enhances the performance of the silver and zinc ions and may substancially reduce the need for supplemental chemical treatments when the spa is not in use.

How often do I replace the cartridge?
If you have a 24hour circulation system that runs all the time,your cartridge will last about 4 months.Look at the beads inside and when all the silver has worn off they turn white.If you have a demand heating system it will probably last about 5 to 6 months.