Does UV Sterilizer Kill Ich?

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There’s never a good time to get an ich infestation in your aquarium. Parasites are like a ticking bomb for your fish, so you must act quickly.

You know you’re in for a tough week, and you’ll have to juggle temperature changes, water changes, medication doses, and possibly a quarantine tank. Anything to get rid of the pest asap!

A UV sterilizer is another much-lauded but uncommon method to kill ich and other parasites. Many aquarists swear by it as a treatment or preventive strategy to guard their fish against parasites. But does UV actually work?

Could it really help you rid your fish of ich and other infections? Keep reading to find out! I’ll provide a more in-depth look at UV systems and their benefits.

I’ll also explain some of the other methods to kill ich.

Does UV Sterilizer Kill Parasites?

UV sterilizers are potent tools that can indeed kill parasites, along with bacteria, viruses, and even algae! They work by emitting a low wavelength light that can penetrate the cell walls of microorganisms.

Once inside the cell, the light alters the organism’s DNA, preventing it from using energy, reproducing, or infecting your fish.

A UV sterilizer can therefore help you get rid of ich and many other parasites. But there’s a catch. This aquarium device only kills external parasites. Internal parasites aren’t exposed to light.

So, if you’re using UV as a treatment, you’ll have to wait until the parasites leave the fish to multiply.

What is UV Sterilizer Used For?

A UV sterilizer is a disinfection method that uses UVC light to kill unwanted organisms in the water column.

It’s a good water-purification method for those who don’t want to use harsh or staining chemicals.

When used in the aquarium, a UV sterilization system can:

  • Get rid of cloudy water due to bacterial overgrowth
  • Clear green or yellow water caused by an algae bloom
  • Reduce the spread of other algae in the tank
  • Prevent parasitic, fungal, and bacterial infections in fish, coral, and invertebrates

Despite the antimicrobial effect of UVC light, UV sterilizers can’t replace filters. You’ll still need a filtration system to keep ammonia and nitrites low.

I should also mention that UV sterilizers are not selective about which microbes they kill.

UV sterilizers are not to be used during tank cycling, as the UVC light can kill the beneficial bacteria growing in the water column.

UV sterilizers might also diminish the effect of active compounds in fish medications.

How to Treat Ich Quickly in Your Fish Tank?

Ich is a life-threatening parasitic infection in fish. If left untreated, it can cause extensive gill damage, suffocating your fish to death. You want to do something about it as soon as you notice symptoms of infection.

Here are some tried and true methods to kill ich in the aquarium:

– Use a UV sterilizer.

Ich infects fish only for a limited time before reemerging into the water column. Once the parasite becomes free-floating, you can kill it nearly instantly with the help of UVC light.

However, you might have to keep the UV treatment up for one to two weeks to ensure all the parasites have left the fish’s body.

– Remove carbon filter media and use ich medication.

There are also tons of medications available to kill ich. Look for products with malachite green, methylene blue, formalin, copper sulfate, or potassium permanganate as the main ingredient.

Such products are highly effective and safe for your fish. Always follow the dosing instructions on the product label.

– Raise the aquarium temperature if your fish can tolerate it.

Ich has a temperature-dependent life cycle. A warmer aquarium will speed up the infective life stage of ich, making it leave the fish’s body faster.

Once out of the fish’s body, the parasite will succumb to the heat and fail to reproduce.

To use this method, bump the water temperature by 1°F every 24 hours. You want to keep the aquarium at a temperature of at least 86°F for two weeks.

This should be enough to kill all the new tomonts in the tank.

– Use a salt treatment if your fish aren’t too sensitive to it.

This method is also highly effective but dangerous for scaleless fish and invertebrates! Make sure you’re using aquarium salt for this.

The ideal dose for treating ich is one tablespoon of salt per 5 gallons of water.

Dissolve the salt slowly and increase the water salinity over a 24-hour period.

Remember to replenish the salt each time you do a water change. Keep up the treatment for ten days maximum.

Can Fish Survive Ich Without Treatment?

It’s highly unlikely for fish to survive ich without intervention. Once infected, a fish will develop only limited immunity.

The ich parasite will continue living in the aquarium, propagating and potentially infecting the fish again.

It also depends on what tissues the ich infects. If the ich attacks the mouth or gills, it’s only a matter of time before the fish succumbs to its injuries.

Severe gill damage inevitably leads to suffocation. Mouth injuries will prevent the fish from feeding properly.

The stress of infection, the lowered appetite, and the wounds on the fish’s body also leave it vulnerable to other infections in the long run.

There’s no good reason to leave the fish battle ich without intervention, especially when multiple affordable and effective treatments are available.

Should You Get a UV Sterilizer for Your Tank?

Do you want a spotless aquarium with crystal-clear water? Are you not a fan of chemical parasite treatments?

Well, a UV sterilizer could serve you well. These aquarium gadgets are gentle with fish but will kill anything that ruins the water quality or threatens your pet’s health.

Of course, UVC light isn’t the only way to get clear water or kill parasites. But unlike other methods, UV sterilization has some unique advantages that make them a worthy investment.

I believe UV has a huge edge over regular water treatments for a few reasons:

– UV sterilizers are versatile tools

Many treatments are available for algae, bacteria, viruses, and parasites. But what about an all-in-one tool that works for all aquarium settings?

UV sterilizers can kill all microorganisms in the water column and can be used in both freshwater and marine aquariums. No need to keep multiple bottles of four or five different water treatments when you have this gadget at home!

– They’re quick, easy, and always on hand

A UV sterilizer is a one-time investment. They indeed cost extra money upfront. But they save you time, stress, and energy in the long run.

You won’t have to set alarms to dose medication around the clock. No need to worry about emergency buying fish medicine either. The UV system is always there when you need it.

– They won’t affect the good bacteria in the tank

Every microorganism that gets exposed to the UVC light dies. This is excellent if you’re dealing with a bacterial infection in the tank. A UV fertilizer will do the exact thing as an anti-bacterial medication.

But unlike medication you put into the water, the UV won’t damage the biological filtration in the aquarium. Luckily for you, the nitrifying bacteria in an established tank live mostly in the filter.

The biological filter media stays covered and hidden from the light. Thus, there are no risks of uncycling your tank.

– They’re perfectly safe for all aquatic pets

Not all fish can tolerate the same medication doses. Most medications also hurt aquatic pets like shrimp, snails, and corals. But not UVC light!

You’re not adding anything to the water when using a UV filter. When used at the right wattage and with the correct flow rate, UV sterilizers are highly safe and effective for all community tanks.

– They help you improve the redox balance effortlessly

The redox balance is an important but less frequently mentioned measurement of water quality. Maintaining a proper redox is crucial for the equilibrium and absorption of minerals in the tank, especially in marine aquariums.

The recommended balance for saltwater aquariums is +300 to -100 mV. Freshwater aquariums also require a value between +125 to -200 mV.

The most well-known way to maintain a suitable redox is by providing dissolved oxygen and positively charged minerals like calcium and magnesium.

A UV sterilization system can also promote a good redox balance by lowering oxidative stress in the aquarium.

– They boost your fish’s immunity

UV sterilization can improve your fish’s health in two big ways. First, UVC light kills pathogens and parasites, which would otherwise attack your fish. Secondly, it maintains superior water quality thanks to its anti-oxidizing effect.

The improved redox balance improves the fish’s immune response and mineral absorption, contributing to long-term health outcomes.


UV sterilizers are highly potent and versatile gadgets. You can use a UV system to kill external parasites like ich within days.

UV also works against any other microorganism in the water, including fungus, bacteria, and algae.

The best part is that UVC light is not dangerous for fish, corals, snails, shrimp, and other invertebrates. UVC light won’t affect the beneficial bacteria in established tanks either, unlike certain medications.

Besides the obvious health benefits, you’ll also enjoy its visual effects. UV sterilization eliminates all foreign microorganisms in the water column, leaving behind only crystal-clear water.

You’ll get rid of dangerous parasites and the unsightly bacterial and algal blooms that often appear out of the blue.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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