Aquarium keepers all understand that their tanks need to be filtered and cleaned regularly to remove potentially dangerous chemicals. Unfortunately, even the best filters and routine water changes won’t eliminate harmful bacteria or parasites that could infect your fish, leading to sickness, stress, and even death. Finding the best aquarium UV sterilizer for your tank can help with this.
Luckily, equipping your aquarium with a UV sterilizer will destroy these harmful organisms and maintain a healthy environment for your tank inhabitants. We’ve tested numerous aquarium UV sterilizers, and our reviews and buyer’s guide below will help you choose the best one for your tank.
Best Aquarium UV Sterilizers:
What is the Best Aquarium UV Sterilizer?
Our all-around favorite aquarium UV sterilizer is the Coralife Turbo-Twist UV Sterilizer Black 6X. Most importantly, it’s powerful enough to kill off algae, bacteria, and fish parasites to maintain a beautiful and healthy tank. It’s also a breeze to set up and adjust, it’s suitable for most tank sizes, and you can use it as a stand-alone sterilizer or an in-line water treatment option.
What is an Aquarium UV Sterilizer?
An aquarium UV sterilizer is a device that uses UV radiation to remove potentially harmful organisms from your tank water. It either hangs on the rear of your aquarium or gets added to your filter lines.
As water passes in front of the sterilizer or through it, the UV radiation denatures the DNA and proteins of any bacteria, viruses, or parasites in the water. This denaturing either kills the organism or destroys its capacity to reproduce, effectively ridding the water of any infection and limiting an outbreak.
UV Clarifier Vs. UV Sterilizer
When shopping for a UV tank treatment option, you’ll very likely run into UV clarifiers and UV sterilizers. There is one crucial difference between the two: clarifiers will destroy algae and bacteria, while sterilizers will destroy algae, bacteria, and parasites.
Both clarifiers and sterilizers will leave your tank free from harmful bacteria and algae that lead to cloudy water. However, sterilizers will also destroy viruses like Ichthyopthirius multifiliis (commonly referred to as “Ich”), Chilodonella, Anchorworm, Flukes, and more.
Benefits of Using Aquarium UV Sterilizers
There are numerous benefits to using UV sterilizers in your tank.
Reduced Chance of Infection
Most aquarists agree that the most significant benefit of using a UV sterilizer in their tanks is destroying parasites and bacteria before they infect their fish and cause an outbreak. All tanks are prone to harboring diseases, some of which can be stressful, time-consuming, and costly to get rid of once they infect your tank inhabitants. This means your fish will be less likely to experience illnesses like ich.
When you use a UV sterilizer, your fish aren’t guaranteed not to experience a bacterial or viral infection, but the chances of infection are significantly lower.
Reduced Rate of Infection Spread
In an untreated tank, a bacterial or viral infection tends to spread from fish to fish and run rampant within the aquarium. Thankfully, UV sterilizers destroy the free-floating organisms and restrict reproduction.
Bacteria and parasites common in fish tanks reproduce very rapidly, so UV sterilizers drastically reduce the rate of spreading and multiplying within your tank.
Whether you purchase a UV clarifier or UV sterilizer, the device will destroy algae that develop in your tank. Tank algae are one of the leading causes of cloudy water, so you can expect noticeably clearer water when you install a sterilizer, usually within just a few hours.
If you choose a UV sterilizer that hangs on the back of your tank instead of being installed in your filter’s lines, the light will be visible in your water. Many aquarists enjoy the vibrant color of the UV light, and it can bring out the natural beauty of your fish, plants, and coral.
Safe for Tank Inhabitants
UV radiation naturally denatures and destroys single-celled organisms like bacteria and even some multi-celled parasites. However, it’s perfectly safe for fish, invertebrates, plants, and coral, so sterilizers are suitable for just about any tank.
Although you’ll still need to perform water changes and clean your filter to ensure no harmful chemicals accumulate in your tank water, a UV sterilizer will afford you the luxury of needing to scrub your tank clean less often.
With a sterilizer, the algae that normally builds up on your tank decorations and glass will be significantly reduced by UV radiation. Your tank will look cleaner for longer and require less effort from you to remain aesthetically pleasing.
Disadvantages of Aquarium UV Sterilizers
Of course, no piece of aquarium equipment is perfect, and UV sterilizers are no exception. There are some downsides to using these devices in your tank.
They Destroy Good Bacteria
Your tank depends on beneficial bacteria suspended in the water and found in your filtration system to cleanse the water. The bacteria in your aquarium break down fish waste and left-over food particles into safer compounds that then get removed during water changes. Nitrobacter is responsible for the nitrogen cycle, which is paramount for the safety and well-being of your fish.
Unfortunately, UV sterilizers will destroy both good and bad bacteria in your tank, meaning some of the beneficial and necessary bacteria will be denatured. Thankfully, much of the healthy bacteria remains in your biological filter media, but any that floats freely in your water will likely be destroyed by the UV radiation.
Any aquarist knows that keeping an aquarium is expensive, and adding another piece of equipment that isn’t absolutely necessary will increase your costs even further. They can pay for themselves over time, but you’ll need to spend some money upfront and also on an ongoing basis.
UV bulbs wear out far more quickly than standard light bulbs, so you will need to replace your UV bulb about every six months. They’re not terribly expensive, but the cost will add up over time.
They Destroy Algae
A UV sterilizer’s ability to destroy algae is a bit of a double-edged sword because some fish and other tank inhabitants rely on algae as a food source. A sterilizer will effectively kill most of the algae in your tank and leave the water looking clearer, but it will also limit the food for any algae-eating organisms in your tank.
They Make Medicine Ineffective
Most UV sterilizers will denature medications and make them ineffective. For the most part, this isn’t a significant issue since the radiation also dramatically decreases the chance of infection. However, a sterilizer will never be 100% effective, and medications will need to be administered in a separate tank without UV treatment to be useful.
Factors to Consider When Choosing Aquarium UV Sterilizers
Not all aquarium UV sterilizers are made equal. There are numerous factors and features to consider when purchasing.
Capacity / Wattage of UV Light
The capacity or wattage of the light you choose will help explain how effectively the UV radiation penetrates your water and how intensely it treats the tank. You can think of the capacity as a strength rating, where higher capacities mean a more comprehensive treatment and better suitability for larger tanks.
Capacity and wattage are also essential to consider because UV radiation won’t be able to penetrate plants, decorations, substrate, or other physical obstructions in your tank. A more powerful light may seem like overkill for a small tank, but it might be necessary for adequate treatment if the tank is very busy.
Flow Rate of the Pump
Whether your sterilizer is set up in your filter lines or behind your filter return, the flow rate of the tank water is important when deciding on a sterilizer. UV radiation takes time to penetrate the water entirely, especially since all tanks will have some floating particles that obstruct the UV radiation.
The faster the water flows through your filter, the less time it will remain in contact with the source of UV light. As such, higher flow rates typically demand a more powerful UV light for proper treatment.
Dwell time refers to the amount of time your tank water and anything suspended in the water will remain under the UV bulb. The longer the dwell time, the more likely the radiation is to provide a complete treatment and entirely sterilize the water.
Dwell time is directly related to the flow rate of your water pump. Faster, more capable water pumps will result in a diminished dwell time and a less complete UV treatment. Conversely, slower flow rates will leave the tank water exposed to UV radiation for longer and will generally deliver a better treatment.
The dwell time required in your tank will also depend on the capacity of your UV bulb. A more powerful bulb will treat an equal amount of water in a shorter amount of time, requiring a lower dwell time for a similar treatment.
UV transmittance refers to how well the UV light can penetrate the water in your tank. Unfortunately, this measurement is particular to your tank and cannot be provided by manufacturers.
UV radiation won’t pass through solid objects in your tank or suspended in your water, which means transmittance — and therefore water treatment — is affected by cloudy water, plants, decorations, fish, and other animals. The more particles in your water and objects in your tank, the lower the transmittance will be and the less effective the UV treatment will be.
For the best results, place your UV sterilizer in-line after filtration or hanging behind your filter return for HOB filters.
Low-Pressure UV Light and Effect of Temperature
The mercury inside your UV bulb will always be under pressure inside the vacuum within the glass. Most aquarium UV sterilizers maintain a low pressure for the best treatment results. Low pressure will result in ample transmittance and power.
However, the performance of low-pressure UV bulbs also depends more on the water temperature, and they deliver far less desirable results in low water temps. Generally speaking, tanks above 68 degrees (F) will benefit most from a low-pressure UV light, while medium-pressure or high-pressure bulbs will be required for colder tanks.
Even though low-pressure UV lights can function at 68 degrees (F), they’re more effective at even higher temperatures.
Some UV sterilizers include a quartz sleeve to insulate the bulb and help maintain a higher temperature. This is especially important for low-pressure bulbs that are more efficient at higher temperatures.
Quartz sleeves will add to the price of your sterilizer, so getting one without a sleeve is a better option if your tank water is warmer than 70 degrees.
Quartz allows almost all UV light to pass through it, so it hardly diminishes the efficacy of the sterilization. However, algae and other particles can accumulate on the outside of the sleeve and make treatment a bit less effective over time.
Types of Organisms
Finally, you should consider what types of organisms you want to eliminate in your tank. If you’re just looking to keep the water clear by decreasing algae and destroy some harmful bacteria, a clarifier might be sufficient for your setup. However, these devices won’t kill parasites and other viruses that can be costly and stressful to get rid of.
For complete protection and the most peace of mind, your best option is a high-powered UV sterilizer that can handle algae, bacteria, and parasites for your tank size and water quality.
How To Install A UV Sterilizer Inside Your Aquarium
Installing a UV sterilizer in your tank is relatively straightforward, but there are some steps to take to ensure it functions properly and provides the best results possible.
1. Determine the Best Location
First, you’ll need to figure out where in your tank the UV sterilizer will do its best work. The UV light works best on clear water with few obstructions. The best placement will depend on the type of sterilizer you buy.
It’s typically best to place a hang-on-back sterilizer very near your filter return because the water coming out of your filter will be the clearest in your tank. This will be the best area for optimal UV transmittance.
If you have an in-line sterilizer, your best option will be in the return line from your canister filter. Again, the water that has just passed through your filter canisters will be clear and free of most debris, providing the best opportunity for UV transmittance.
2. Attach it to the Pump (or Canister Filter)
Once you’ve determined the best location for your sterilizer, you can attach it either to your filter pump, canister filter, or simply the edge of your aquarium in the case of a HOB sterilizer. If you’re connecting your sterilizer to a filter, ensure that the tubes are correctly connected and that there are no leaks when you turn on the pump and the device.
3. Turn on the Power
Finally, turn on the UV sterilizer, and reactivate your pump or filter.
Best Aquarium UV Sterilizer Options
Below, we’ll include the best UV sterilizers based on our extensive testing. We’ll offer a brief list of our favorites, followed by an in-depth review of each.
- Coralife Turbo-Twist UV Sterilizer Black 6X
- COODIA Internal Green Water Killer Filter Aquarium Tank U-V Pump
- Aqua UV 15 watt Advantage 2000+ Hang On UV Sterilizer
- SunSun JUP-01 9W UV Sterilizer Submersible Filter Pump
- Green Killing Machine GKM24W Internal UV with Power Head
- Aqua Ultraviolet AAV00339 Twist UV Sterilizer for Aquarium, 25-watt, Black
- Lifegard AquaStep Pro 15 Watt UV Sterilizer Model
This UV sterilizer can work as a hang-on-back option or as an in-line device, so you can adapt it to just about any tank.
It has a robust flow rate and the ability to adjust it based on your tank size.
It removes algae, bacteria, and parasites, making it an excellent option for keeping your tank water clear and free of potentially harmful organisms.
It’s a bit on the expensive side, but its adaptability and high power capability are unmatched.
- It has an adaptable flow rate to fit any tank
- It has a HOB option and an in-line option
- It’s a powerful and effective sterilizer for all harmful organisms
- It removes algae and keeps water clear
- It has an LED light to let you know when it’s on
- It’s relatively expensive
- The bulbs can burn out rather quickly
This is a hang-on-back sterilizer that cannot be adapted to work as an in-line device. It’s ideal for use with a HOB filter as well.
The unit is a bit bulky, so it will take up quite a bit of space within your tank.
It has a decent flow rate that will be sufficient for smaller volumes, but it won’t be suitable for tanks larger than about 20 gallons.
This sterilizer is very affordable, so it’s likely to fit into just about any aquarist’s budget.
- It includes a quartz sleeve for better functionality
- It’s very effective for removing algae
- It’s very affordable
- It has a good flow rate ideal for smaller tanks
- It can only be used as a HOB sterilizer
- It takes up quite a bit of tank space
This sterilizer uses the return as the hanger, so it only functions as a HOB sterilizer. It cannot be added as an in-line device.
It’s very powerful and will be suitable for just about any tank size. The high-powered bulb can even handle sterilization for small ponds.
It’s very efficient for removing algae, bacteria, and protozoa, so it’s great for maintaining clear, healthy water.
It’s very costly, but it’s one of the most powerful UV options we tested.
- It features a very powerful UV bulb
- It has an outstanding flow rate
- It can handle most tank sizes and even small ponds
- It clears water very rapidly
- It will kill off bacteria and parasites to keep your tank healthy
- It cannot be set up as an in-line device
- It’s very expensive
This is a submersible UV sterilizer, so you’ll have to take up some tank space with it and keep it on the inside wall of your aquarium.
The flow rate is outstanding, and some fish might not enjoy the heavy current it creates in the water. However, this does mean that it’s suitable for larger tanks and even small ponds.
The clearing capacity is wonderful, and you can expect it to remove greenish coloring from algae in just a day or two. It will also remove bacteria and parasites with outstanding efficiency.
This pump is very affordable.
- It includes a powerful pump capable of treating large tanks
- It comes with a powerful UV light that helps maintain very healthy water
- It’s powerful enough for us in large tanks and small ponds
- It removes algae rapidly and maintains healthy water
- It only functions as a submersible sterilizer
- It takes up quite a bit of tank space and may detract from your tank’s appearance
This is a submersible sterilizer that will take up some space inside your tank. It cannot be used as an in-line or HOB sterilizer.
It includes a mechanical filtration option to supplement the UV treatment. It’s very adept at clearing algae and cloudiness from your tank water.
It doesn’t include a quartz sleeve, so it’s best for use in warmer tanks.
This unit is very affordable, and it can handle tanks up to about 100 gallons.
- It includes mechanical filtration media as well
- It features a very powerful flow rate
- It’s very affordable
- It clears water rapidly
- It helps maintain a healthy and aesthetically pleasing tank
- It takes up quite a bit of space inside your tank
- It’s only suitable for warmer tanks over 68 degrees (F)
This is an in-line sterilizer only, so it’s only suitable for tanks that use a sump pump or other external filtration method. It could be adapted to a canister filter, but the connections are made for PVC pipes.
It’s extremely powerful and will make quick work of even the largest tanks. It clears out algae, bacteria, and parasites, leaving you with clean, healthy water.
This sterilizer has an excellent flow rate and power capacity, but it is very expensive and will be prohibitively costly for many hobbyists.
- It has hook-ups for sump pumps and other plumbing systems
- It includes a mighty UV bulb capable of treating large volumes quickly
- It’s suitable for extra-large and crowded tanks
- It maintains clear water and reduces the risk of infection
- It is very expensive
- It isn’t ideal for use with canister filters
- It cannot function as a HOB sterilizer
This sterilizer can function as a submersible device or an in-line option, so you can customize it to your tank and setup.
It has an excellent flow rate of 450 GPH, but it’s not adjustable. As such, it’s suitable for tanks up to 200 gallons but won’t be ideal for smaller aquariums.
It has a powerful UV light that will clear up your water quickly and help limit the spread of bacteria and parasite infections.
This UV sterilizer is rather expensive.
- It can be used as a submersible sterilizer or as an in-line device
- It uses a method of triple exposure that ensures your water is treated optimally
- It’s excellent for large and crowded tanks
- It clears water and removes harmful organisms quickly
- It’s not ideal for smaller tanks
- The flow rate cannot be adjusted
- It’s rather expensive
Aquarium UV Sterilizer FAQs
How long should a UV sterilizer be on in an aquarium?
Many sterilizers can stay on 24/7, but this treatment is considered overkill in most cases. Ideally, you’ll leave them on until your tank water is transparent and then run them a few hours a day thereafter for maintenance. This will extend your bulb’s lifespan.
Can you use a UV sterilizer in a planted tank?
Yes! UV light is perfectly safe for planted tanks. It will help manage algae accumulation and will help keep your tank beautiful and clean.
Can too much UV light kill fish?
UV light kills single-celled organisms like bacteria and parasites that are harmful to your fish. However, the light won’t kill your fish, even if it shines directly on them.
Are UV sterilizers bad for plants?
Most UV sterilizers are enclosed and won’t shine on your plants. Even if they do, your plants won’t be negatively affected. UV sterilizers are perfectly safe for plants.
How long does it take for UV light to kill algae?
The time you’ll need to wait before your water is crystal clear will vary based on your tank size, how cloudy it is, and the specifications of your sterilizer. Most tanks with a UV sterilizer will see a noticeable improvement in 48 hours and will be perfectly clear within five days.
Will a UV sterilizer kill snails?
No, UV sterilizers are safe for invertebrates, including snails, shrimp, crayfish, and crabs.
Will a UV sterilizer kill brown algae?
Your UV sterilizer will kill off free-floating brown algae. Introducing a sterilizer to your tank and then doing a good manual cleaning will ensure most brown algae are removed. Your sterilizer will prevent brown algae from growing back.
UV sterilizers are wonderful tools for limiting algae growth and maintaining a healthy environment free of parasites and bacteria that could be harmful or even deadly to your tank inhabitants. They will clear up your water and reduce the risk of infection in your fish, ultimately saving you time and frustration in the long run.
Our all-around favorite sterilizer is the Coralife Turbo-Twist UV Sterilizer Black 6X. It’s powerful and can be adapted to just about any tank. It has HOB and in-line options, and the flow rate can be adjusted for different tank sizes and requirements.