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If you’ve ever had a mysterious breakout of some kind among your fish, you may be wondering what you can do to prevent it in the future. Do you need a UV sterilizer or some kind of cleaning equipment?

There are things you can add to the aquarium system that can help – having the right filtration is the first step, setting up a fish tank with live sand and live rock helps, as well – but what if the basics aren’t doing it?

Enter the best UV sterilizer, a device designed specifically to kill of nasty the little microorganisms you can’t see in your aquarium water, although they may show up via cloudy water.

Best UV Sterilizer Quick-Find Table

Image Product

  • Easy to install and use
  • Fast-acting
  • Guaranteed performance, if sized properly
  • Easy to install and use
  • Fast-acting
  • Guaranteed performance, if sized properly

  • 99.99% effective
  • Disinfection in 30 minutes
  • Easy installation and operation
  • 99.99% effective
  • Disinfection in 30 minutes
  • Easy installation and operation

  • Very fast-acting
  • Simple and effective use and control
  • Doesn’t need to be run constantly
  • Very fast-acting
  • Simple and effective use and control
  • Doesn’t need to be run constantly

  • Approx. 8000 life hours for bulb
  • Can run without creating bubbles
  • Great for turtle tanks
  • Approx. 8000 life hours for bulb
  • Can run without creating bubbles
  • Great for turtle tanks

What is a UV Sterilizer?


Simply put, a UV – or Ultraviolet – sterilizer is used to control infections by stopping the spread of unhealthy microorganisms from one fish to a coral or invertebrate or other fish.

This spread happens through the water – much like infections happen through the air for humans and mammals – as well as via things like free-floating algae.

When used correctly, these UV sterilizers kill off the microorganisms before they can spread. These bad guys have to be in the water, though for the sterilizer to work.

Top tip: The UV light will not kill organisms attached to fish or corals – they must be free-floating.

How does a UV Sterilizer Work?

UV tank sterilizers use a germicide fluorescent lamp that creates light at a wavelength that irritates and kills of algae.

The water and algae pass over the bulb – or around it, if a quartz sleeve is used – and is irradiated by the wavelength of light.

The light penetrates the algae and bacteria, and as it does so, the DNA mutates and prevents the growth and multiplication of said nasty organisms.

What Factors Influence the Effectiveness of a UV Sterilizer?

Dirty aquarium with fishes - UV sterilizer

There are several things that affect the effectiveness of an aquarium UV light.

Type and Size of the Organisms

First, the size and type of organism can determine whether or not the UV sterilizer for fish tanks will work. 

Author note: Ultraviolet light can kill viruses, algae, bacteria, and protozoa, but some require much higher doses to do them in. Plus, some bacteria are more resistant to UV radiation than others.

Bulb Power of the UV Sterilizer

The power of the UV bulb also has a significant affect on how powerful the affects will be on those nasty killers in your aquarium. The wattage of the bulb will tell you the amount of UV light that’s created by the bulb.

Bulbs with higher wattage create more UV light, and the ability of the germicidal fluorescent bulbs to produce the light decreases with age over time. In most cases, you need to replace the bulb about twice a year. 

UV light is also produced by higher temperatures – between 104 and 110-degrees Fahrenheit – while cooler lights will produce less UV radiation.

Penetration of the UV Light

If the UV light can’t penetrate the water, it won’t be able to kill off the algae and organisms. High water turbidity decreases penetration.

You should place the ultraviolet aquarium filters after the biological and mechanical filter media within your filtration system so that the water is cleared by the time it reaches the UV bulb.

Also, salinity affects the effectiveness of UV light on the organisms. UV light penetrates freshwater better than it does saltwater.

Finally, the cleanliness of the sleeve or bulb also affects this power of the UV. If there’s a salt deposit or film on the bulb or sleeve, the light won’t penetrate as fully and won’t be able to irradiate the bacteria.

Contact Time of water to uv sterilizer

Finally, the amount of time the UV light has to work on the bacteria makes an impact on its power. The more time, the more bacteria killing power you’ve got.

Contact time is changed drastically by the flow rate of the water in your aquarium.

Top Tip: While you’re treating the aquarium for such issues, you should probably consider reducing the water flow rates to help increase the contact time the UV filter has with the water.

Why Would You Need a UV Sterilizer?

planted-tank-with-fish-best-uv-sterilizer-for-fish-tanks - UV sterilizer

Since the cleanliness of the aquarium has a huge impact on how healthy your aquarium is, the UV sterilizer is a potentially vital part of your system.

UV sterilization is a safer way to kill of bacteria, algae, protozoa, et cetera than some other methods, because it won’t kill your fish. For us, that’s obviously a huge deal.

So, if you’re seeing some unhealthy outbreaks in your tank, you definitely should consider using a UV sterilizer to help those fish, corals, and other critters out.

UV sterilizers are efficient and beneficial as long as you match the sterilizer power properly to the size of your aquarium and power of the water flow.

If the water flow is too strong, for example, the light exposure to the water will be too short and the efficiency will be dramatically reduced – and it won’t be able to kill the microorganisms you’re trying to eradicate.

If the flow is too slow, on the other hand, the process will take too long and reduce efficiency overall as well. Match the power of the flow to the UV light power.

Benefits of using a UV Sterilizer

UV Sterilizers Don’t Kill Fish

Unlike some other cleaner and sterilizer products out there, a UV sterilizer doesn’t kill your fish. They’re also safe for corals, invertebrates, and plants.

Top tip: Just be sure to follow the instructions that come with your particular model to avoid damaging your eyes.

a UV Sterilizer can Kill Malicious Bacteria but Not Beneficial Bacteria

If installed and used properly, the UV sterilizer in your tank will only kill the malicious bacteria in your aquarium instead of the beneficial bacteria.

How? Because the beneficial bacteria lives on rocks, gravel, driftwood, etc. and the malicious bacteria is what’s flowing around in the water.

Author note: Be aware that UV sterilizers cannot save infected fish, plants, etc. If they have a disease, the UV sterilization will not “cure” them. It only helps to prevent others from becoming ill.

Drawbacks of using a UV Sterilizer

UV radiation is an effective killer for bacteria and other microorganisms, but there are some potential drawbacks.

a UV Sterilizer Only Works in Clear Water

detail of cleaning of home aquarium, collecting the pieces of plants and algae after pruning with a net.

First off, UV light is only effective in clear water. If your tank is mucked with visible algae and murky water, you’re going to need to clean the water accordingly.

Sometimes, this will clear up on its own, and sometimes it won’t. There are ways to treat this with a little time.

But since the fish tank water must be clear for the UV filter to work, you need to deal with that before beginning UV treatment.

UV Light Works in Tandem with Other Filtration But Not By Itself

UV lights work in tandem with other filters but does not replace them. UV cannot remove contaminants like copper or lead.

Other filter media must be used for this – or an RO system – which means UV lights add to your cost of the base for your little aquarium ecosystem.

UV Light Systems Need Electricity

You’re already powering multiple other devices to keep your aquarium running.

The water pump, air stones, filter, LED light system, and various other devices that you may or may not opt for are already adding a bit to the energy bill. Adding on another device that uses some power increases that.

Most are designed to run efficiently, but they still do add some energy use.

How to Choose the Best UV Sterilizer Aquarium System

There are a few things you’ll want to do before making a purchase on a UV sterilizer.

Do Your Research

First you need to do your research. Learn about UV sterilization, how affective they are for situations in fish tanks like your own, and whether or not there are any suited to your specific needs.

Be sure to read loads of UV sterilizer reviews to verify each one actually lives up the claims made – real-life users tell it like it is, usually, and tend to keep you up-to-date on any bad batches going out at the moment.

Consider Your Tank Size


UV sterilizers come in specific sizes to match specific fish tank sizes and flow rates. Learn which ones are suitable for the gallons of water in your fish tank you have.

Determine Which Type of UV Sterilizer Would Work Best in Your Setup

Much like filters, there are both in-line UV sterilizers and HOB – hang on back – options that may or may not suit your needs, depending on your exact situation.

There are also submersible options which may also be the best choice for your aquarium, depending on aesthetics, size, placement, et cetera.

Keep your aquarium shape and aquascape in mind as you consider.

HOB sterilizers and submersible sterilizers are usually small and convenient – easy to install – while in-line sterilizers tend to be larger and more powerful.

Reviews of the Best UV Sterilizers For Freshwater and Saltwater Aquariums

As we dug through the many options for the best submersible UV sterilizer and the best UV sterilizer for reef tanks (among all the other options!), we found quite a number of choices to consider.

We looked through each with you in mind, using these criteria to determine which ones are actually effective – and not just paying someone advertising fees to a high-rating.

We considered which ones are suitable for different types of aquarium settings. We looked for the following things in each product:

  • High-quality materials and manufacturing process
  • Well-trusted brands in the industry
  • High review ratings from real-life aquarist hobbyists
  • Effectiveness in doing the job – i.e. they actually do kill off the bacteria you’re trying to get rid of
  • Ease of use
  • Ease of installation and maintenance

#1. Aqua UV Advantage

Aqua UV 15 watt Advantage 2000 Hang On UV Sterilizer

The Advantage Series Aqua UV HOB Sterilizer is the best overall choice in UV sterilizers for aquariums. It’s a lightweight, hang-on-the-back unit that installs easily, quickly, and conveniently.

It’s effective at quickly sterilizing the water and killing off the green water caused by algae and the other crud that gets in there, and it’s easy to use and maintain over time.

  • Type of UV sterilizer: HOB
  • Tank size: Up to 85 gallons
  • Best for: Freshwater aquariums

What We Loved

The UV sterilizer from the Advantage Series Aqua is a really great little machine. It mounts easily and quickly on the back of your aquarium.

It’s slim and lightweight so it’s non-invasive and doesn’t effect the aesthetics of your fish tank much – if at all.

It’s easy to connect up the sterilizer, simply by connecting into the return line or pump.

That makes this a really fantastic option for anyone, especially beginner hobbyists just learning how to use all of the various types of equipment in aquariums.

The 15-watt bulb is pretty powerful and really does the trick. Many folks have noticed a dramatic difference in their aquariums within just three to five days, thanks to this little beauty and the power of the bulb.

It’s best used for small and medium sized aquariums, up to 85-gallons in size.

Plus, we love that this is an American made product, so we know it’s high-quality and not some chintzy hunk of chunk chucked out of some factory overseas where quality control isn’t as important.

What We Didn’t Love

There is really only one issue we have with this UV sterilizer: the bulb doesn’t last a super long time.

It has to be changed semi-frequently – every 4 or 5 months, depending – and that can be a little tiresome.

Otherwise, it’s great! Just don’t use in a saltwater tank. It’s designed for freshwater aquariums.

Our Verdict on the Advantage Series Aqua UV HOB Sterilizer

Overall, the Advantage Series Aqua UV HOB sterilizer is a great, simple product. It does what it’s supposed to, and it does it well. It works quickly, quietly, and helps clear up the gunk pretty fast.

Be sure to only use it in freshwater tanks, though, and check the bulb every couple of months to make sure it’s still working.

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#2. TAISHAN UV Sterilizer


The Taishan UV sterilizer is a great small tank UV sterilizer that’s perfect for beginners and folks looking for a basic, easy,
budget-friendly model for a smaller tank.

The model’s biggest claim to fame is the stated 99.99% effectiveness rate on killing malicious bacteria in your aquarium.

  • Type of UV sterilizer: Submersible
  • Tank size: 20 to 50 gallons
  • Best for: Small freshwater tanks
  • Bonus features: Easy
    install suction cup brackets

What We Loved

There are lots of things to love about this little UV sterilizer from Taishan. The first and foremost being the effectiveness of it when installed and used properly.

The light is super easy to mount inside your aquarium as well, which is a huge bonus, especially for folks just getting started out or kids who’re learning how to care for their pets.

We love quickly the Taishan works as well – effectively killing 99.99% of malicious bacteria in 30 minutes or less.

We love that this one works in green water, as well, unlike some models that have to have a cleaner tank to clean.

You just use the light for 3 to 4 hours a day every 2 to 4 days for keeping the tank clean and bacteria free. And since it has a timer, you can set it up to do so without a lot of hassle.

It’s made of strong silica glass for long-lasting quality.

The Taishan is extremely easy to install and use as well, which is great.

What We Didn’t Love

There’s not much to complain about on the Taishan. Though a couple of things stood out.

First, they give strong cautions against shaking the light as it will potentially cause a short circuit. So, if it’s handled with care, it should be fine. If, however, it’s not, well… Not a great situation.

The other thing isn’t specific to this product but more that I feel, again, the need to give the caution that you must ensure you have the right size tank for using with this product to avoid problems.

Our Verdict on the Taishan UV Sterilizer

Ultimately, this is probably the best beginner UV sterilizer for small tanks we could recommend. It’s easy to use and install and does the trick.

The one main caution given, though, is that even though this is a beginner’s type of equipment piece, it must be handled with care to avoid the machine being broken and shorting out.

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#3. SunSun Jup-01

Sun Sun

The SunSun JUP-01 Submersible UV Sterilizer Filter Pump is a great option, especially for saltwater fish keepers with small aquariums.

It does the trick in getting rid of the free-floating bacteria in there, and does it all without tubing or an additional circulation pump.

  • Type of UV sterilizer: Submersible
  • Tank size: Up to 75 gallons
  • Best for: Small saltwater & freshwater aquariums
  • Bonus features: Comes with a built-in pump

What We Loved

The SunSun JUP-01 is a fantastic option that has so many great positives that it’s definitely a top-three. For starters, it comes with a built-in water pump, so you don’t have to get a pump, too, in your aquarium.

This saves time and energy, as long as you use it all properly.

Secondly, you don’t need any extra hardware to setup the system and keep it running.

It’s easy to mount the UV sterilizer with the suction cups that come with it – and they actually work – and that’s it. Mount and go.

And you can either mount it horizontally or vertically, depending on which is going to be the least invasive for your aesthetics and setup.

And finally, and potentially most importantly, this UV sterilizer, when used properly, actually works for saltwater aquariums.

What We Didn’t Love

There are two things that we don’t necessarily love about this one.

The first is that it’s not designed for large tanks. This isn’t too big of a deal, except that because it’s the best UV sterilizer for saltwater tanks, that’s a little frustrating for those with marine tanks larger than 75-gallons.

The second is more problematic, but still workable. Several people we talked to reported that the motor burns out after prolonged use.

The solution for this is doing what others have tried: running it initially to clear everything up, then only using it a couple times a week to maintain a clear, healthy tank.

Our Verdict on the SunSun JUP-01 Submersible UV Sterilizer Filter Pump

If you’ve got a saltwater aquarium, this is the UV sterilizer for you. It’s easy to mount, easy to maintain, and comes with its own water pump to help direct the water easily through the UV filter for the best contact time and cleaning action.

Just be sure to run it steadily upon installation to remove any outbreaks of microbes and bacteria, and then run it infrequently – say twice a week – to preserve the motor from burnout from over-use.

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For a mid-sized saltwater or freshwater fish tank, the COOSPIDER Sun is a great choice in UV sterilizer. The UV sterilizer has a flow rate of 210 gallons per hour, working on tanks between 40 and 80 gallons in size.

It’s great for getting that cloudy water to go away in a short period of time without much work on your part.

  • Type of UV sterilizer: Submersible
  • Tank size: 40 to 80 gallons
  • Best for: Saltwater or freshwater tanks
  • Bonus features:

What We Loved

The effectiveness on cloudy fish tanks is one of the first big things we noticed about this. It will kill the cloud (though not algae that’s attached!).

It can be used both in freshwater and saltwater tanks, equally effectively – and it gets the job done quickly, efficiently, and quietly. Most reports are 1 to 3 days for cloud removal.

You can adjust the device to prevent bubbles, if you prefer (or need) the tank to go without, plus you can adjust the direction of the water flow, as needed, to suit the needs of your stock.

It’s easy to setup and operate, which always important in our book.

What We Didn’t Love

The primary issues we noticed on this one were user error, not product glitches so much.

The light comes with a sponge around it. This must be removed before use. There is also a silicone piece on the end of the light bulb that must be removed.

Once folks remove these packing materials, most of the complaints disappear.

The device must also be completely submerged to work properly and some folks seem to miss that note.

Our Verdict on the COOSPIDER Sun

The COOPSIDER Sun isn’t a fancy product, but it’s an effective one that will get the job done in your mid-sized aquarium, whether preventative or removing the cloudiness after it’s happened.

It’s easy to install and use, it’s highly adjustable, and it works. That’s the main thing – it works. Just be sure to remove packing materials for proper effect.

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Runners Up in Freshwater UV Sterilizers

Two other UV sterilizers worth mentioning include the GRECH CBG-800 5W UV Sterilizer Hang-On Back Filter combo and the Coralife Turbo Twist UV Sterilizer.

Both are great for freshwater aquariums, though didn’t quite make our top list.

The GRECH CBG-800 provides a 211 gph filter flow rate and works on tanks between 20 an 50 gallons in size.

The combination helps to keep the water contact longer while giving you an adjustable water flow.

It can be used with either freshwater or saltwater, but I’d generally just recommend for freshwater tanks or smaller saltwater aquariums only.

The Coralife Turbo Twist works for tanks up to 250-gallons.

It has a nice little indicator light that lets you know when the bulb needs changing and works for either in-line or hang on applications.

It uses a twist-flow design, which is also great, as that increases the contact time over most others and creates a nice, natural water flow for your fish and plants.

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