UV vs ozone in RAS: which do you need?
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UV sterilizers
A UV sterilizer passes water past UV-C lamps. The light inactivates bacteria and other pathogens without adding anything to the water. It sits on the return line, after solids removal, because particles shield pathogens from the light (Aquaculture International).
Ozone generators
An ozone generator makes ozone, a strong oxidiser. It is dosed into a side stream, usually through a protein skimmer, where it breaks down dissolved organics and colour. The ozone reacts before the water returns to the fish.
They work better together
Ozone clears colour, which lets more UV light through the water. In a USDA study, ozone raised the water’s UV transmittance (USDA ARS). That is why systems with high colour gain the most from ozone ahead of UV.
Side by side
| UV | Ozone | |
|---|---|---|
| Main job | Inactivates pathogens | Oxidises organics and colour |
| Adds to water | Nothing | Ozone, dosed and controlled |
| Position | Return line before tanks | Side stream, with a skimmer |
| Needs | Clear water, lamp replacement | Dose control, ventilation |
| Typical use | Most RAS | Dense, marine and shrimp systems |
Which do you need?
- Most farms: UV on the return line.
- Marine and shrimp: UV, plus ozone with a protein skimmer.
- Dense freshwater with colour build-up: consider adding ozone.
Ozone needs care
Ozone is harmful to fish and people at high levels. It must be dosed into a side stream, given time to react, and used in a ventilated room. We include dose control in the design.
See the disinfection overview.
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