Its name says it all. The Green Killing Machine is an internal UV sterilizer designed to efficiently kill or inactivate any floating organisms, reducing green algae and water cloudiness. It comes in various sizes suitable for aquariums of up to 50 gallons and boasts a very simple installation. Suction cups allow for a no-frills, no-tools installation even behind aquarium décor, while the slow flow rate maximizes sterilizing time and improves the UV efficiency. Furthermore, a mechanical pre-filter sponge captures debris and optimizes UV exposure. We also like the convenient LED control box that signals when you need to replace the 9W bulb. Suitable for freshwater and saltwater aquariums, this is one of the best internal UV sterilizers.
Suitable to use in freshwater or saltwater aquariums as well as in garden ponds, the SunSun UV sterilizer is another noteworthy submersible unit. It provides simple and effective control of floating microorganisms, and it comes preassembled. Ready to use straight out of the box, it requires no additional tubing or circulating pump. Various sizes make it ideal to use in setups of up to 75 gallons. Like the Green Killing Machine, it comes with a built-in pump that directs waterborne organisms past the lamp, and it’s equipped with a large mechanical pre-filter sponge that captures debris and improves sterilization. Suction cup mounting brackets allow for vertical or horizontal installation either in your aquarium or in the sump.
Designed for ponds and big aquariums, the Jebao Clarifier is an external UV sterilizer that comes with bulbs of various sizes, between 13 and 55 watts. It’s perfect for the outdoors and resists cold weather beautifully, so you can have a clear pond or outdoor aquarium water all season long. The powerful bulb ensures effective management of all waterborne microorganisms; although it lacks a pre-filtration sponge, it’s incredibly effective. It’s easy to install and requires minimal maintenance. Three types of fittings also make it easy to incorporate into an existing filtration system. The UV clarifier bulb has long lifespan, and overall, this is one of the best outdoor UV sterilizers you can get your hands on.
Next entry on our list of the best aquarium UV sterilizer styles, we have this hang-on-back clip-on unit. The smallest brother of the Green Killing Machine by AA Aquarium, it delivers the same efficiency but at a smaller scale. It comes with a 3W UV bulb, and it’s perfect for systems of up to 20 gallons. The simple clip-on installation makes it easy to attach to any waterfall filter for quick and simple sterilization. Small but efficient, it controls green water and bacteria. Just like its bigger brother, it has a LED that signals when it’s the time for a bulb replacement.
Last but not least, the Aquatop In-Line UV sterilizer is one of the most versatile units you can find. It can be installed either in-line or hang-on, and it can work alone when paired with a pump or powerhead or as an in-line component of a canister filter unit. A 10-watt bulb delivers proper sterilization and quick removal of floating microorganisms. The replaceable lamp has long lifespan, and it works wonders in fresh- or saltwater tanks of up to 200 gallons. Capable of providing clear and healthy water in most systems, this UV sterilizer can surely help your aquatic creatures to thrive.
If you’re tackling the idea of getting a UV sterilizer for your aquarium…
… perhaps you’re wondering what styles there are available.
Based on their position in the water flow, you can choose from:
In-line sterilizers: Are plumbed into the main aquarium filtration system and occupy the last position in the line, after the mechanical filtration unit. Most in-line units are designed for larger aquariums and incorporate higher wattage bulbs than the hang-on sterilizers.
Hang-on sterilizers: More compact than the in-line, these sterilizers are designed to be mounted on the back of the tank and work as an independent device fed by a submerged powerhead, although some models connect to the return line of a canister or in-line filtration systems. They are very easy to install and maintain and are ideal for smaller aquarium setups.
Internal sterilizers: These are placed inside your main tank or sump, submerged in the water. No extra plumbing required, but you may need to figure out a cleaver way to hide it.
External sterilizers: These are mostly used for larger aquariums and ponds. They have the advantage of being more discreet but require more connections.
Orientation-wise, you can pick from vertical or horizontal units. When choosing, keep in mind that some horizontal units can be be installed vertically, but all vertical sterilizers allow for vertical installation only.
An avid goldfish breeder and keeper for nearly 20 years, Meredith Clawson is the founder of the Pure Goldfish website and author of the book The Truth About Goldfish. Pure Goldfish has been featured in Wikihow, Wikipedia, The Aquarium Guide and more.