Boyu · UV clarifier
Submersible UV Steriliser
- UV lamp
- 4–20 W
Knocking out a green water bloom or running in a sump on a larger system.
6 models
Gear catalogue · 10 uv & sterilisers
Aquarium uv & sterilisers, compared properly
UV clarifiers and electrolytic units for green water and algae. From Boyu, Chihiros, Eheim, Oase, SunSun, Twinstar. Match them to your tank, then put up to four side by side.
TL;DR, choosing aquarium uv & sterilisers
A UV clarifier kills free-floating algae and bacteria as water passes a UV-C lamp, which is why it clears green water in days. It does nothing for algae growing on plants, glass or hardscape, and it does not fix the cause, which is usually too much light or unbalanced nutrients. Electrolytic units like Twinstar and Chihiros Doctor work differently, using a small current to discourage algae spores. Treat any of them as a helper while you fix light, CO2 and nutrients, not as a cure.
How to choose
- Size the lamp wattage and flow to your tank; too much flow through a UV cuts its effect.
- Plan to replace UV-C lamps about once a year.
- Electrolytic units suit nano and medium tanks and need regular cleaning.
- Fix the cause of algae alongside, see the algae ID guide.
Chihiros · Electrolytic
Doctor 5
Freshwater planted tanks where you want algae prevention and a temperature alarm in one small gadget.
1 model
Chihiros · Electrolytic
Doctor Mate
- Tank size
- up to 125 L
Nano and small planted tanks, including shrimp tanks, that want an algae and bacteria hedge.
1 model
Chihiros · Electrolytic
New Doctor
Mid-size and larger planted tanks where you want an extra tool against algae alongside good maintenance.
2 models
Eheim · UV clarifier
reeflexUV
- Tank size
- 80–800 L
- UV lamp
- 7–11 W
Planted tanks prone to green water, or anyone wanting a bit of extra clarity and pathogen control.
3 models
Eheim · UV clarifier
reeflexUV+e
- Tank size
- 300–2000 L
Larger planted tanks where you want UV only for set hours, or want it tied into an Eheim digital setup.
4 models
Oase · UV clarifier
ClearTronic
- Tank size
- up to 600 L
- UV lamp
- 7–11 W
Canister-filtered tanks prone to green water, or keepers who want an extra safeguard against outbreaks.
3 models
SunSun · UV clarifier
AUV UV-C Lamp
- Tank size
- up to 2600 L
- UV lamp
- 3–14 W
Tanks or sumps with green water or where you want to cut free-floating bacteria.
6 models
SunSun · UV clarifier
ZUV Timer UV-C Lamp
- Tank size
- up to 2600 L
- UV lamp
- 10–14 W
Large tanks and sumps with green water.
3 models
Twinstar · Electrolytic
Nano Sterilizer / Algae Inhibitor
- Tank size
- 19–250 L
Planted tanks up to about 250 L where you want an extra hedge against green water and algae, especially during the first months.
4 models
Frequently asked questions
Straight answers to the questions people ask most when choosing aquarium uv & sterilisers.
Does a UV steriliser get rid of algae?
It clears green water (algae floating in the water). It does not remove hair, spot or black beard algae growing on surfaces.
Is UV safe for plants and fish?
Yes, the light stays inside the unit. Some keepers note it can break down a little of the iron from liquid fertilisers, so dose in the morning and see how your plants respond.
Do electrolytic algae devices work?
Many keepers report fewer algae problems in nano tanks with them, but results vary and they work best alongside good light and nutrient balance.
How long should I run a UV clarifier?
For green water, continuously for a week or two while you correct the cause. Some people then run it permanently as prevention.
Keep reading
Other gear
Specs come from the maker or a major retailer’s listing and are checked where we can. Makers revise products, so confirm the figures on the product page before you buy. Product photos are supplied by the brands and their distributors.