Ozonizer (Sander)
Erwin Sander GmbH
A corona-discharge generator that makes ozone (O3) from air and feeds small, ORP-controlled doses into a skimmer or reactor, oxidizing dissolved organics so water loses its yellow tint and ORP climbs.
Why it mattered
Ozone arrived with the German school of reef keeping — Sander, the skimmer pioneer, also made the reference ozonizers — and use surged in the mid-1990s, with a second wave around 2005. The draw was water you could see through: ozone shatters the large organic molecules that yellow water and that skimmers remove poorly.
Running ozone properly was a small discipline of its own: an air dryer to keep output up in humid rooms, ozone-safe plastics, carbon on the output to catch residuals, and an ORP controller dosing to a target near 400 mV rather than running open-loop.
The technology never disappeared, but its jobs got divided up — UV took sterilization, carbon took color removal, and both are simpler to live with. Ozone remains the connoisseur's polisher, respected and debated in roughly equal measure.
Key specs
- Corona-discharge generation from dried air
- Output rated in mg/hr (Sander P 2000: 2,000 mg/hr on dry air)
- Humidity can cut output by about half without an air dryer
- Typically dosed through a skimmer or dedicated reactor under ORP control
- Effluent air and water passed over carbon to remove residual ozone
Keeper notes
- Keepers who ran Sander units in the 1990s call them temperamental: output sagged as air dryers saturated, and ozone degraded some plastics.
- Modern users typically run ozone briefly to an ORP target rather than continuously, and report visibly clearer water.
- Skeptics argue everything ozone does well is covered by carbon and UV with less risk and upkeep.