kardan

Hi All, Is there anyone use ozonizers at discuss tank ? What must be the mV range for crystal water without harming the fish ? My tank 350Lt. 2x external filter total cap is 2.300Lt/hr, 1x13Watt ultraviolet. Ph appx 6.5, GKh below 5, Kh below 3. 25+ athletic still healty discus fish. Have an ozonizer 250mg/hr capacity. Do not know how to use without disturbing fish. Regards, Oner