How UV Works
UV-C light (254nm wavelength) damages DNA in passing microorganisms — bacteria, parasites, viruses, free-floating algae.
Water must pass close to the bulb at slow flow rate. Fast flow = inadequate exposure.
What UV Treats Effectively
Green water (free-floating algae) — clears in 3-7 days.
Free-swimming parasite stages (ich theronts, velvet swarmers).
Reduces bacterial counts in tank water.
What UV Does NOT Treat
Disease on fish bodies (UV cannot reach attached parasites).
Internal infections.
Algae growing on glass or rocks.
Cloudy water from fine particulates (no living organisms to kill).
Sizing and Use
Match wattage to tank: 8W per 50 gallons for parasite control. 4W per 50 gallons for water clarity only.
Replace bulbs every 12 months — output drops sharply after 12-14 months.
Run continuously, not just during outbreaks.
- ✦Position after mechanical filtration — clean water passes easier
- ✦Quartz sleeve must be cleaned every 3-6 months
- ✦UV does not affect beneficial bacteria in filter media (those are attached, not free-swimming)