I use ozone. It keeps the water clean, pale blue, and smelling fresh. Livestock also seem to like it, if one can determine that to any real degree. I have the Ozotech generator from BRS, set to nominal output of 80 mg/hr, controlled by Apex and calibrated ORP probe. Air pumped in through a silica air dryer, O3 resistant tubing after the ozonizer, feeds into its own port on my skimmer silencer. There's a bag of carbon hanging directly in the path of skimmer water outflow, and a large carbon-filled cap sitting on top of the skimmer to filter its effluent air. At first when this tank was new, I ozonized aggressively, but with time the amount of ozone needed to maintain an ORP of just under 400 has dropped to around 2 hrs total per day, and I no longer directly couple O3 generation to ORP level, but am using a timer now instead.
Ozone makes some people nervous due to potential human toxicity, but there are a few things to mitigate that concern. First, O3 tends to stay where it forms and decays quickly. Second, it has the odd feature that it degrades even faster when it has to pass through narrow openings. Meaning, closed cabinet doors are exceptionally good at killing it. Third,
meters are available that will constantly read the ambient O3 level; sort of like the CO (carbon monoxide) meter you may already have. 6' away from my aquarium, mine has never read more than the first green bar. Although if you put it in the sump while the ozone is on, remove the skimmer carbon cap, and close the cabinet door, it reaches maximum red within minutes.
