How to Choose an Aquarium UV Sterilizer: The 5 Best of 2021 Reviewed

If you are a reader of FishTankWorld, you may have noticed that we talk a lot about fish tank water quality. The simple reason is that without clean water, your fish can't breathe. You cannot have a thriving aquarium if your water isn't clean. Poor water quality opens your fish up to diseases and parasites that can kill them. UV sterilizers are one of the best ways to keep your fish tank clean.

In this guide we will discuss how aquarium UV sterilizers work, their benefits, how to install one, and how to maintain one. We've also reviewed our picks for the 5 best UV sterilizers for fish tanks on the market. Hopefully you will find this guide to be helpful!

Among the strong competition some UV sterilizers are bound to be better than others. After carefully reviewing the field we have compiled the list below. In our opinion, these are the highest quality and best priced UV Sterilizers for fish tanks on the market.

The Aqua UV Advantage 2000+ features the latest in UV sterilizer technology. It is an extremely high capacity UV sterilizer and is best suited for small ponds, large freshwater fish tanks, and medium sized saltwater aquariums.

In freshwater tanks, this unit is capable of flowing 700 GPH for 30,000 µw/cm2. This makes this sterilizer ideal for 200-500 gallon freshwater tanks. In saltwater tanks it can flow 233 GPH for 90,000 µw/cm2 a5-200 gallons, which makes it ideal for 75 gallon saltwater aquariums. It is also capable of clarifying a 2,000 freshwater pond or water gardens.

If you value space but want an effective unit, then this sterilizer would be a great choice. Its dimensions are 18" x 4" x 2.5" and it weighs only 4 lbs. It’s lightweight and rather slim profile will allow it to fit onto the back of your tank easily.

As far as working fast is concerned, this UV sterilizer will clear your entire tank in a span of about 3-5 days. Some people have even reported that it cleaned their entire aquarium overnight.

The design is a simple but elegant hang-on-back design. The manufacturer offers a 1-year warranty and even guarantees that it will clear up your tank if it is sized, installed, and operated correctly.

Note: You will need either a pump or a canister filter to operate this UV Sterilizer. Also, if the rim on your aquarium is more than inch wide you will have to find another way to mount this sterilizer.

Bottom line, this is a top-notch UV sterilizer. Whether you have a 75 gallon reef tank or a 500 freshwater tank, this UV sterilizer will clear up your tank's water in no time!

If you’re looking for a simple yet very effective way to clean a 75-gallon tank, the best-selling Green Water Killer is an excellent choice. This is the number-1 selling UV sterilizer on the market and it's easy to see why. With its advanced UV sterilizing technology, simple design, affordable price, internal pump, and the fact that it is quite literally a green water killer, this 5W UV sterilizer our top-pick for 50-75 gallon sized tanks.

The unit has a replaceable 5W bulb that kills harmful microorganisms and free floating algae. The Green Water Killer can turn green cloudy water crystal clear in just 3-5 days! This UV sterilizer comes with has strong suction cups so it won't fall down and an adjustable outlet so you can control the direction of the flow coming out of it.

Unlike some other models, this sterilizer doesn't require any special plumbing. This is an in-unit sterilizer that goes directly into your tank and has its own internal pump for pumping water through the bulb housing. Its small size and lack of external plumbing make it easy to hide behind an ornament or plant.

This units simple design and in-unit pump make it quick and easy to install. Replacement bulbs are easily available and relatively affordable.

Bottom line, the 5W Green Water Killer is a fantastic UV sterilizer for medium-sized fish tanks. If you purchase this unit it will have your 50-gallon saltwater or freshwater tank sparkling clear and free of algae in just a couple of days. You don't have to just take our word for it though, check out all these other 5-star reviews!

The SunSun 9W UV Sterilizer is another good option to consider when looking at UV sterilizers. This unit measures 12" H X 3.3" W X 3.75" L and flows around 210 gallons per hour. This makes it suitable for reef tanks and freshwater aquariums up to 75 gallons.

This is an in-tank unit so no additional tubing or pumps are required. To install, all you need to do is take it out of the box, put it in your tank, and plug it in. It comes with suction cups, which can be used for mounting the unit horizontally or vertically.

The UV bulb on this unit easily kills any harmful microorganisms and free floating algae in your tank. In most situations, you will begin to see positive results within just a few days time.

Some other nice features of this unit include the fact that it only requires 1 power outlet and that replacement bulbs can be purchased relatively cheaply. For optimal performance it is recommended that the UV bulb is changed annually.

This UV sterilizer is compatible with freshwater fish tanks, saltwater reef aquariums, and even outdoor ponds.

Note: The pump on this unit is quite strong and it can be overkill for smaller tanks. Unfortunately there is no way to adjust the water flow.

Bottom line, the SunSun 9W UV Sterilizer is a great UV sterilizer for 50-75 gallon tanks but would probably be overkill on anything less than 50 gallons. Check out these additional reviews.

The SunSun JUP-23 is a 13W UV sterilizer and is best suited for 75-150 gallon freshwater and saltwater tanks. At 13.5" H x 3" W and 2.5" L this unit is just slightly larger than the 9W one. The powerful 13W UV bulb will easily kill any harmful microorganism and free floating algae within days.

Like the smaller unit, the JUP-23 is a plug-and-play UV sterilizer. Simply drop it in your tank and plug it in. The suction cups allow you to mount it horizontally or vertically.

Some people have reported broken glass bulbs upon delivery. The manufacturer has started packing the inside of these units with bubble wrap as a result. Make sure you check the bulb and remove any bubble wrap prior to installation!

Another nice feature of this unit is the adjustable flow nozzle, which the smaller unit doesn't have. Like the 9W unit, replacement bulbs for this unit are fairly inexpensive.

Bottom line, if you have a 75-150 gallon tank that is cloudy or experiencing an algae bloom, the SunSun JUP-23 13W UV Sterilizer is a strong choice. And the low price simply can't be beat!

The Coralife Turbo Twist UV Sterilizer is an inline unit that is designed to be installed after your canister filter. It comes in variety of sizes including a 9W unit designed for up to 125 gallon tanks, an 18W unit for up to 250 gallon tanks, and a large 36W unit designed for tanks up to 500 gallons.

The Turbo Twist features a quartz glass sleeve and a unique twist-flow design that causes increased water exposure to the UV light and helps kill free floating parasites, algae, and bacteria.

Being an inline unit, it does require some extra plumbing to install as well as a pump to move water through it. The 36W unit requires a pump capable of flowing at least 300-900 gallons per hour. The canister does come with mounting brackets if you want to hang it on the back of your tank.

While we personally have not experienced any leaks with this unit, some people have reported leaks that have led to electrical shocks. Given the relatively high price, as well as the reported electrical issues, we would recommend the Aqua UV 2000+ over this unit for 100-500 gallon tanks.

Just like every other living animal on Earth, fish a susceptible to sickness and disease. The difference with fish is that is difficult to treat them if they get sick. In addition, infections tend to spread fast in confined spaces. You can only watch it spread through the aquarium and hope for the best. This is where a UV sterilizer can come into play.

This is possible because UV is mutagenic to viruses and bacteria on certain wavelengths (particularly from 260nm-270mn). This means that the UV breaks the molecular bonds in the DNA of microorganisms and causes them to die.

No, in fact, UV sterilizers are generally considered beneficial. Fish have a natural resistance to UV light so it does not harm them at all when they’re exposed to it. In fact, without it, their pigment tends to be under-stimulated. That’s why you’ll notice that fish exposed to UV light tend to have more vivid colors whereas those that aren’t tend to be paler. This is because UV light stimulates the pigment to move faster and reflect more light.

If you’re medicating your fish, remember to turn off the UV light, as it makes the tank completely sterile and will kill the medication as well. Another situation in which it might be better to switch your UV sterilizer off is when you are cycling a new aquarium. Because UV light will kill any free floating organisms exposed to it, it will also kill any beneficial bacteria in the water column that passes through your sterilizer.

Watch this video for more information on some of the benefits of UV sterilizers.

The good bacteria in your tank can be found in live rocks, bio filters and in the substrate of your aquarium. This means that a UV sterilizer won't kill the good bacteria as it is not free floating in the water column.

As was mentioned before, the primary advantage of using a UV sterilizer is that they can get rid of all the potentially harmful microorganisms in your fish tank. It’s inevitable that your aquarium will eventually run into issues with diseases or parasites, especially when organisms other than fish also live there (algae, for example). Using a UV sterilizer can help solve and prevent this problem. Even if you clean the fish tank regularly, parasitic activity can occur.

Before getting a UV sterilizer you should read up on the different types of units on the market and how they work (hopefully this is why you're here!). There are 3 types of UV sterilizers - the tray type, tube type-wet bulb, and tube type-dry bulb. The difference between the last two is that the wet bulb is not lined with quartz. If the water system is cold, you should get a UV sterilizer with a quartz sleeve because it makes periodic cleaning and bulb replacement easier.

UV sterilizers also come in a hang-on design, which is simply hung on the inside of your aquarium, or an inline design, which can be plumbed into your filtration system.

Choosing the right unit for your application will depend on what type of tank you have (saltwater or freshwater) and its size. Your tank size determines how much water flow the UV sterilizer needs to be able to support. Manufacturers tend to provide tables with recommended maximum aquarium size and the appropriate flow rate for all of the models they have.

Keep in mind that manufacturers take different things into account and that that’s why ratings can differ despite having the same wattage. For instance, some use a 100% bulb efficiency while others only account for 60%, or they can refer to clear or turbid water.

Other variants may refer to the type of organism aimed to be killed - bacteria, algae, or protozoa.

The UV sterilizer should be set up after everything else in your aquarium has been set into place and your tank has cycled. If you're installing an inline UV sterilizer it should be placed inline after your filtration system and any heat exchanger. Most UV sterilizer units have hose barb connectors to connect to the appropriate water pump. If this isn’t the case, then it’s most likely that the unit has an add-on connector as a PVC slip fit or a barb hose attachment. Whichever unit you purchase should also come with an installation guide that you can follow.

Maintenance requirements for UV sterilizers will depend on the type of device you choose and the type of aquarium you are running.

UV sterilizers lined with quartz will need to be taken out once a month and cleaned with rubbing alcohol. If the unit is larger, chances are high that it will have a self-wipe mechanism to make cleaning easier. If you use the UV sterilizer regularly, you’ll probably have to replace the bulb every 6 months, but check the manufacturer guidelines to be sure.

Nothing beats the feeling of looking at a crystal clear aquarium with brightly colored fish, rocks, corals, and/or plants. If you're experiencing a cloudy tank or an algae bloom, nothing is going to clear up your tank's water faster, and keep it that way, than a high-quality UV sterilizer.

If you have an aquarium around 200-500 gallons, then the Aqua UV Advantage 2000+ is our top recommendation for you. On the other hand, if your aquarium is 75 gallons or less, then we are going to recommend the best-selling COODIA Green Water Killer.