How Long Should You Run a UV Aquarium Sterilizer?

5 min read

Depending on your aquarium size and need, you may have used a UV sterilizer within your tank. The joy of all fish owners is to keep their fish happy and stress-free despite not being in their wild environment.


Most fish owners often attempt to simulate the natural environment of their fish species. One of the ways to achieve successful wild-environment simulation is proper lighting consideration.

There are different recommended times for running UV aquarium sterilizers, as most opinions depend on fish species and consumer preferences. However, running your UV aquarium sterilizer for 24 hours would be best.

All fish species need light, although to a varying extent. Some fish need a long exposure to light while some require little exposure to keep them light tolerant.

Aquarium lights perform various beneficial functions, thus generating questions about the recommended running time for a UV aquarium sterilizer since it is, in fact, light.

Running your UV sterilizer for 24 hours will guarantee efficient delivery of microorganism-free filtered water into your tank. In addition, some aquarium owners specify running the aquarium sterilizer for periods less than 24 hours.

Why Should You Run Your UV Aquarium Sterilizer for 24 Hours?

The primary reason why people install a UV sterilizer in their aquarium is to combat and kill unwanted microorganisms like algae, bacteria, and other parasites.

You need microorganisms like algae in your tank because they help to generate oxygen and stabilize the aquarium environment for your fish. But when the algae grow excessively in number, they do more harm than good.

Algae will now compete with your fish and other beneficial bacteria for essential nutrients, negatively affecting your fish’s health and performance.

You can regulate your fish’s daily performance routine by running the UV light for 24 hours. This is achievable because the fish’s natural pigment protects against harmful UV rays.

You don’t need to worry about running the sterilizer all the time since it is designed to work that way when installed and used correctly.

How Does A UV Sterilizer Work in Your Aquarium?

UV aquarium sterilizers are designed to remove any unwanted microorganisms from your tank.

It is well known that the major source of aquarium contamination comes from the water entering the aquarium tank.

Therefore passing the water meant for your aquarium usage through a UV sterilizer will kill all microorganisms in the water.

Suppose you want to achieve total tank water sterilization; in that case, you must pay attention to the water contact time with the UV bulb.

Since more prolonged exposure to UV rays means higher UV penetration, most UV sterilizers have a bulb around which the water will flow.

The water must flow slowly near the bulb and along its full length before proper sterilization can be assured.

If you run a large amount of water through the UV sterilizer, the UV rays may not be able to kill all the microorganisms contained in the water because of the low contact and exposure time.

What Should You Consider Before Choosing Your UV Aquarium Sterilizer?

The two significant parameters to consider before purchasing your UV light sterilizer are the UV bulb capacity and aquarium tank size.

To maintain efficient water sterilization, you must match the optimum water flow to the proper UV light capacity.

For example, you can not use a UV bulb with a 15-watt capacity to successfully sterilize a strong water flow because the water will be in contact with the UV light for only a short period.

How Do You Maintain Your UV Aquarium Sterilizer?

Maintaining your UV aquarium sterilizer is not too different from the way you clean and maintain your tank filter.

If you want to maintain your UV light for a long time, you should always clean the pump to avoid blockage and clean its crystal sleeve.

The UV sterilizer sleeve is a distinct barrier between water and light. Thus, if it gets covered with dirt, the UV light won’t be able to penetrate the water effectively and thus reduces the sterilizer’s life span.

Depending on the UV sterilizer you use in your aquarium, you need to change the UV bulb every six months or beyond.

This process is essential because it helps to maintain and keep the UV radiation energy within the optimum range needed to achieve efficient sterilization.

You should always filter your tank water before passing it through the UV sterilizer. This is necessary because the suspended matter contained in the water may absorb or scatter the UV light.

When you pass unfiltered water through the UV sterilizer, the microorganisms suspended within this matter may bypass the UV exposure and infect your fish.

When Should You Stop Running Your UV Sterilizer?

It is best to run your UV sterilizer for 24 hours, but there are conditions where you need to turn off the sterilizer.

It is not advisable to turn on the UV light before adding fish into your tank to avoid re-introducing parasites into the aquarium tank and to avoid harming your fish.

Moreover, it would help if you didn’t run the sterilizer before seeding your tank with beneficial bacteria.

This is important because turning on the UV light before adding beneficial bacteria into the tank may harm the bacteria’s growth since the UV light radiation can kill them.

It is also not advisable to run the UV aquarium sterilizer while using medication to treat infection within the tank.

Many people argue that the UV ray will kill the infective organism. Still, many don’t know that doing so will also neutralize the medication used to treat the water.

Should You Filter Your Water Before Running The UV Sterilizer?

Yes. You should filter the water you intend to pass through the UV sterilizer because the suspended matter in such water may reduce the efficacy of the UV sterilization process.

When you use unfiltered water, some microorganisms may survive the sterilization process because they are not exposed to UV radiation due to obstruction created by dirt and suspended matter.

Since most aquarium owners use tap water in their aquarium, such unfiltered water usually contains iron and other suspended particles that can absorb or scatter UV radiation.

Thus, you need to filter the water before running it through the sterilizer.


Aquarium UV sterilizers are crucial to fish health.

You must run them every time to protect your aquarium fish from non-beneficial bacteria, algae, and other parasites.

While running your UV sterilizer, you should maintain proper water flow and UV bulb capacity to sterilize your tank water successfully.

Written by:

Pet Aquariums

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