A koi pond is a beautiful addition for fish lovers and gardening enthusiasts. However, preventing algae growth in such ponds can be an issue without proper equipment, such as ultraviolet light. We’ve put together a list of the Best UV Light for Koi Ponds here to help you maintain and avoid algae in your ponds.
Comparison Table
 Top Top Top Top | TotalPond Complete Pond Filter with UV Clarifier | 4.3/5 | PrimeEligible | View on AMAZON | |
 Top Top Top Top | PONDMASTER 40W UV Clarifier | 4.1/5 | Prime | View on AMAZON | |
 Top Top Top Top | OASE Vitronic 36 UV Clarifier for Pond | 4.3/5 | PrimeEligible | View on AMAZON | |
 Top Top Top Top | Aqua UV 57 Watt 2 " UV Sterilizer | 4/5 | Prime | View on AMAZON | |
 Top Top Top Top | Jebao PU-36 Pond Clarifier | 4.4/5 | PrimeEligible | View on AMAZON | |
 Top Top Top Top | Coralife Turbo-Twist UV Sterilizer 3X, Up to 125 Gallons | 4.4/5 | PrimeEligible | View on AMAZON | |
 Top Top Top Top | Tetra Pond GreenFree UV Clarifier- ponds Up to 8800 Gallons | 4.5/5 | PrimeEligible | View on AMAZON | |
 Top Top Top Top | OXYFUL 18W Non-Submersible UV 14" Light Clarifier- Aquarium/Koi Pond | 4.4/5 | Prime | View on AMAZON |
UV sterilizers prevent the water in your koi pond from turning green. Excess food causes the growth of algae, bacteria, parasites, viruses and other microorganisms, making the water less clear and full of bad smells. Ultraviolet light can clean the water and maintain a healthy environment for your koi fish.
Is UV Light Needed for Koi Ponds?
UV lights, also referred to as clarifiers or sterilizers, are designed to remove algae and bacteria from pond water using electromagnetic radiation. They all work towards create a healthy, clean environment for the plants and fish in your koi pond. However, these machines are designed to kill everything, even the beneficial bacteria.
Clarifiers and sterilizers work in a similar way. Each is equipped with a high-quality UV lamp lights, which is protected and contained by a quartz glass sleeve. The difference between the two is the intensity of the light from the lamp.
A UV clarifier generally has a more intense lights than the sterilizer. The water should flow through the sterilizer more slowly, which increases UV exposure.
UV lights presents electromagnetic radiation and has a wavelength from 10 nm to 380 nm. Organisms in water can be damaged by ultraviolet radiation. These include diatoms, bacteria, parasitic protozoa and floating algae.
Such things will die once exposed to the UV pond filter. Dead cells will clump together and get stuck on the screen. This works to improve water clarity and reduce cloudiness.
The thing to remember is that a UV sterilizer or clarifier is not a pond filter, but they are usually paired with a mechanical or biological filter, which clears debris out of the pond.
Best UV Light for Koi Pond Reviews
1. TotalPond UV Pond Clarifier
If you have a pond with up to 2000 liters of water, the TotalPond UV Pond Clarifier may be the most beneficial for you. It works to clean the greenery produced by algae and prevents the formation of harmful odors.
This clarifier can be installed directly in the pond, or out of the water depending on your preference.
It comes with a 9W UV lamp that can take up to 8,000 hours. The manufacturer recommends replacing the lamp every year for optimal performance.
There is a UV indicator light that will illuminate when the device is operating and it has clear adapters so it’s easy to see that everything is working smoothly.
The water is pumped into the UV chamber just before it’s filtered (filter sold separately). This means that all bacteria die and are then automatically filtered.
Benefits
- Flexible installation
- Easy to remove for cleaning
- Operation is clear
Cons
- Possibly not enough pipes
2. Pondmaster Ultra-Violet-Light Pond Water Clarifier
The Pondmaster has a 20 watt UV lamp to kill floating algae and keep your koi pond looking aesthetic and clean.
This clarifier can be used in a 3000 liter pond with a pump up to 1800 GPH. It is also possible to immerse the pre-purification installation directly in the water or to use it in line with your pump.
You will find that the Pondmaster water purifier has a vortex-flow design with a slim diameter ensuring greater efficiency. The product pushes water through quickly, but leaving enough time in the chamber to kill the algae and bacteria.
Although the product is all in one and has everything you need, it helps to know what you are getting. The 20 watt lamp is good for 9,000 hours of continuous use. However, you can set it on a timer so it doesn’t run all the time.
Benefits
- Vortex flow design
- Installed directly into water
- Slim design
Cons
- Requires a pump (sold separately)
3. OASE Vitronic 18 UV Clarifier
The OASE Vitronic 18 UV Clarifier is a simple and versatile option designed to work with any filtration system. However, it works best with BioSmart filters (5000 – 1000).
Whether you have a new or existing pond system, this product can be integrated to work with it, clearing the green coloring caused by algae and bacteria.
The high-quality UVC lamp guarantees a long service life. It also has constant irradiation, which makes it more effective.
The lamp has clear tube adaptors and a visual inspection window at the top, meaning you can easily look in and check everything is working effectively.
A quick release function makes it easy to open and close the unit, making cleaning the quartz glass or replacing the lamps easy.
Benefits
- No drilling or filing is required
- Long lamp life
- Visual inspection window
- Easy to clean
Cons
- Can trip circuit breaker
4. Aqua UV 57 Watt 2 Inch UV Sterilizer
Most products are designed to be sterilized or rinsed, but the Aqua UV 57 Watt 2 Inch Sterilizer is not. It can purify fresh water up to 3,000 liters with a flow rate of 3,200 GPH.
It is also possible to flush up to 6,500 liters, making the product ideal for aquatic gardens and koi ponds. In addition, it can sterilize salt water up to 355 gallons at a flow rate of 1066 GPH.
The robust design makes installation easy and requires little maintenance. You may need to take it apart to regularly clean the inside and replace the lamp.
The manufacturer claims that Aqua Ultraviolet rays can clean water in just five days. However, severe algae build-up can take a little longer.
You will find this product works well if you have 50 to 75 percent plant coverage in partial shade. This is ideal for many configurations.
Benefits
- No other products / chemicals needed
- Easy installation.
- Sterilizer and clarifier in one
Cons
- Minimum 5 days to clean water
- Possible leakage problems over time
5. Best Overall: Jebao 36W Aquarium Koi Fish Pond UV Light Sterilizer
The Jebao 36W Aquarium Koi Fish Pond UV Light Sterilizer is our best recommended UV light for medium size ponds. It features a 36W UV lamp to effectively remove algae, bacteria and viruses, keeping the pond clean for healthy koi fish. The suction power is approximately 4400 liters per hour and the sterilizer is recommended for a tank of up to 8,000 liters.
This option is quite easy to install and use. It’s not that big and easy to disassemble, so maintenance is very easy. And for best performance, it’s recommended to replace the lamp once a year.
Please note that Jebao 36W is for external use only. Don’t put it in the water, but install it in line behind a water filter.
Benefits
- Effectively removes algae, bacteria and viruses.
- For ponds up to 8000 liters
- Easy installation
- Easy maintenance and use
Cons
- For external use only
6. Coralife Turbo-Twist UV Sterilizers
Coralife Turbo-Twist UV Sterilizers are great for koi beginners. It’s an easy to install, easy to use, and easy to maintain UV sterilizer that doesn’t overcomplicate the UV light process.
Coralife Turbo-Twist has a rotating-flow design that increases water exposure to UV lights, maximizing cleaning effectiveness. It has an indicator light that helps you know if the sterilizer is on and you can easily hang Coralife Turbo-Twist or install the sterilizer online.
This sterilizer works with both fresh and salt water.
The main drawback of Coralife Turbo-Twist is the suction power, which is considered low. Recommended for up to 250 liters of water.
Benefits
- Rotary flow design
- Good for beginners & easy to install
- Can be hung or installed online
- Works with fresh and salt water
Cons
- Low suction power
7. Best For Smaller Ponds/Tanks: Sun Powerhead with UV Sterilizer
The Sun Powerhead with UV Sterilizer is our first choice for small koi ponds and fish tanks up to 75 gallons. It’s low power – 13 W for UV lights and 8 W for the water pump.
The unit is a powerhead, air bubbler and UV sterilizer all in one.
Overall, the Sun 13W UV Sterilizer is compact, lightweight and versatile. It is very easy to install and use, effectively cleaning algae and micro-organisms, preventing your pond from getting green water.
This sterilizer option is also a good choice for beginners. It can pump at a rate of 211 gallons an hour.
Benefits
- Compact, lightweight and versatile
- Clean the tank up to 280 liters (75 gallons)
- Bubbler feature
- Low running cost
Cons
- Recommended for small ponds/tanks only
8. TetraPond GreenFree UV Clarifier
The TetraPond GreenFree UV Pond Clarifier is a series of heavy duty UV pond lights that completely remove algae within 5 days of use. It offers UV resistance for ponds of various sizes, from 660 liters to 8800 liters. Models designed for the smallest ponds work with 5W UV lamps and the larger ones with 36W UV lamps.
The UV light on this model can last continuously for 11 months and it is recommended to be replaced at least every 2 seasons for maximum efficiency.
Unfortunately, no hose is provided for the inlet and outlet valves, but a 3/4 inch or 1 inch pipe is recommended, along with clamps to secure it in place. The inlet and outlet valves are located on either side of this UV clarifier.
The clarifier is not submersible and must be kept above water. It has an excellent 3-year warranty in case of problems and has a great, robust design.
Benefits
- High-efficiency UV bulb
- 3 year warranty
- 4 sizes (660 gallons-8800 gallons)
- Easy installation
Cons
- Must be assembled well to prevent leakage
- Not submersible
- No hose for inlet/outlet valves
9. Sunsun CUV-118 UV Light Sterilizer Pond Water Clarifier
Updated 11th April 2022: This product is currently not available on AMAZON.
The Sunsun CUV-118 UV Light Sterilizer has an 18 watt bulb that makes it suitable for a pond up to 5280 liters.
It can be used with a pump up to 660 GPH. So you can use it in freshwater and marine applications. This makes it ideal for koi ponds and water gardens.
If you want to avoid green water in your pond, it is ideal to work with a sterilizer and clarifier. That way you can maintain optimal conditions for your water source.
This product is of great value because it is a large unit. It’s design is built to be sturdy, strong and lasting. It also works exactly as it says.
Benefits
- No chemicals needed
- Little maintenance required
- Sturdy design
Cons
- Results may take awhile
- Shorter life span
10. Oxyful Non-Submersible UV Ultraviolet Sterilizer Light
The Oxyful Non-Submersible UV Sterilizer Light works well in saltwater tanks, ponds and freshwater aquariums. This product keeps nitrate levels low, leaving a crystal clear water environment.
The UV lamp is of high quality and delivers professional power. This helps prevent harmful bacteria without using chemicals.
This model will kill protozoa, algal blooms, pathogens and cyanobacteria. Along with parasites, free-floating microorganisms, insect larvae, and more. This naturally makes it ideal for invertebrates, saltwater corals and koi ponds.
This oxygen sterilizer and clarifier has a maximum flow rate of 792 GPH and is ideal for a 6604 gallon pond or tank.
The UV lamp is designed to last up to a year. It cannot be submerged, however water can flow in without a problem.
The hard plastic housing ensures that the water is not exposed to the copper. Copper can be dangerous to koi.
Benefits
- Long life UV lamp
- Works with fresh and saltwater
- Chemicals not needed
Cons
- May not be suitable for cold environments
- Not submersible in water
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Before Installing a UV Light in a Koi Pond?
There are a number of things to consider when installing the UV system. Knowing the flow rate and where the light will be installed is quite important. Along with knowing how much space there is between the water ports and the lamps.
Read the description of the manufacturers recommendations carefully for the UV light model you choose to ensure it best suits your pond and other addition equipment.
In theory, it is better to buy a model that has more power than you think you need. Most brands listed here have multiple sizes. If you have a 3,000 gallon tank, you may want to move to the next size just in case.
The product you choose comes with a manual, but in most cases, you should place the sterilizer in front of the filter so that dead algae can be removed from the pond immediately
How Long Does it Take for Ultraviolet Light to Clean a Pond?
When the water is mature, you will notice a change in the water within a week. However, it can take up to two weeks for complete clarity to be achieved. Depending on the severity of the green water, timing can vary slightly.
Final Thoughts
If you have noticed that your koi pond is cloudy or green, it means that there is too much algae. It’s quite common, but it also means that you cannot enjoy or provide a healthy environment for your koi. We believe choosing the Best UV Light for Koi Pond is a worthwhile investment for your fish.
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