ORP is "oxididation reduction potential". It is a measurement of the available oxidization ability of the water. Usually, a "normal" tank will run between 280 and 350, when ozone is injected, the ORP, is raised and the water looks ( to some) to be clearer and some of the inhabitants seem healthier. To look at it another way, Ozone is bleach for your water. If you raise the Orp too high, 450 or more, you may bleach corals and see damage to the fish's gills.
Raising the ORP by injecting ozone is something you should do a LOT of reading about before trying.
As far as the reactor question, Aqua controller or reefkeeper would be a cost decision for me. My reactor just runs on a controler and works just fine.
Good luck.
Chuck.
