Message Forums

faq | etiquette | register | my account | search | mailbox
# Message Forums
L# General
 L# Technical Tinkering
  L# All you ever wanted to know about UV Sterilizers
 Post Reply  New Topic
SubscribeAll you ever wanted to know about UV Sterilizers
Fish Master
Posts: 1515
Kudos: 2354
Votes: 4
Registered: 09-May-2003
male usa
UV Sterilization is the safest method of preventing and eliminating problems in an aquarium, or pond. UV will not kill a parasite on the fish, but parasites go through a free floating stage, at which point they are eliminated. UV Sterilization will also kill free floating algae in the aquarium. Additionally, corals and fish can and do carry bacteria that can infect and spread throughout the tank, killing other inhabitants. The initial thinking on reef tanks was to avoid UV, to keep plankton alive. However, with the skimmers and pumps used on aquariums the plankton population in the water column is virtually non-existent.

UV is more commonly used on Saltwater tanks but their use in FW Aquaria and ponds is increasing. You can use a UV continuously (recommended) or just keep one at the ready, in the event of an outbreak.

Points to ponder about UV Sterilization
 Most effective when run 24/7.
 Most effective if the water is clear.
 Most effective if bulb is new, or replaced regularly (at least every 6-8 months).
 Most effective if the UV light penetrates less than one inch of water.
 Effectiveness can be hindered if the water passes too fast past the bulb. Most effective if the exposure time of the water to the UV light is longer than one second.
 The effectiveness of UV light can be hindered if there is light blockage, i.e. a salt encrusted or dirty bulb.
 Because it can destroy beneficial microscopic organisms that some reef tank inhabitants may depend on as a food source, UV light should not be run during feeding time.
 It can help to prevent future water borne pathogen recurrences, once the initial problem as been completely eradicated from the aquarium.
 UV light not only kills unwanted organisms, but beneficial ones as well.
 It only destroys organisms that are free floating IN the water as it passes by the UV light, i.e. it will NOT get rid of an ich infestation that is already ON fish, or cure a bacterial disease fish may have.
 Should never be run when treating with any drugs or medications.
 UV can also alter the structure of some dissolved chemical compounds.
 UV light can be damaging to the human eye, so DO NOT look into the bulb.
 Always unplug the unit when working on it to prevent possible shock if it breaks or gets wet.

What is UV Sterilization?
What exactly is UV Sterilization? It's actually a very simple process for removing unwanted free floating bacteria and parasitic organisms, like ich, out of your water by passing the water through Ultra Violet (UV) light. Ultraviolet water purification lamps produce UV-C or "germicidal UV," radiation of much greater intensity than sunlight. Almost all of the UV lamp's output is concentrated in the 254 nanometers (nm) region in order to take full advantage of the germicidal properties of this wavelength. UV light is only capable of killing microorganisms such as bacteria, viruses, molds, algae, and yeast. The end result is the organisms die, eradicating your aquarium water of these unwanted nuisances.

How about UV Sterilizer safety?
UV Sterilizer light can be damaging to the human eye so DO NOT look into the bulb. Always unplug your unit when working on it to prevent possible shock if it breaks and gets wet. Also be sure to have water flowing through the unit before you plug it in as the bulb can overheat and explode.

Who needs a UV Sterilizer?
UV Sterilizers are recommended for saltwater aquariums, ponds and larger tanks with sensitive fish.

What can I kill with a UV sterilizer?
-UV sterilizers will destroy protozoan parasites such as Ich during the new born, free swimming life cycle stage of the parasites. NOTE: They do not kill or remove the Ich parasites once attached to the fish.

-UV Sterilizers will kill free floating algae. It will not kill algae that is stuck to your glass or imbedded on your plants, live rock or substrate. It needs to go through the UV sterilizer to be zapped.

What influences the effectiveness of a UV sterilizer?
1. Wattage See the "UV Sterilizer Wattage" chart below for general recommended wattages for your different sizes of aquariums. (These are some conservative estimates that may differ with the recommendations of the manufacturers. See the Flow Rates at the bottom of the right column for comments about the discrepencies between manufacturers with regards to tank size recommendations.)

2. Contact time (dwell time). The longer it takes for water to pass the bulb, the greater the contact time. For this reason the longer the uv sterilizer bulb, the better. Also, this is a good reason not to use a pump that more powerful than is recommended--the water will pass the uv sterilizer too quickly to maximize the effectiveness of the UV radiation.

3. The Age of the Bulb. The uv sterilizer bulbs need to be replaced every six months.

4. Light Blockage. The uv sterilizer bulbs are contained in quartz sleeves. These sleeves will need to be cleaned periodically to prevent light blockage.

Can UV Sterilizers have negative effects?
Yes. UV can alter the structure of some dissolved chemical compounds (especially copper), so you do not want to run your UV sterilizer when treating your aquarium with any drug or chemical medication.

Depending on the cleanliness of the water going into the uv sterilizer, you may need to clean it. Specifically, the outside of the quartz tube that the bulb is set in is what needs to be cleaned. If the UV light from the bulb can't penetrate the sleeve, then it won't reach the water that flows around the quartz sleeve.

Flow Rates:
The recommended flow rates and required wattage for tanks may not seem consistent between manufacturers. The Emperor 25 Watt UV Sterilizer is rated for 125 gallons. The Aqua Ultraviolet 25 Watt UV Sterilizer is rated for tanks up to 100 gallons. The Rainbow LifeGard 25 Watt UV Sterilizer is rated for 200 gallons. The Coralife 18 Watt for 250 gallons. The Custom SeaLife 18 Watt for 100 gallons. Some of this may be because the manufacturers are measuring things differently. For Example: Emperor Aquatics' recommended flow rates are based upon when UV Sterilizer lamps are operating at their 60% end of life efficiency. Additionally, flow rates may be comparing apples and oranges because they may be referring to the effective kill rates of different organisms. Ideally you will choose a UV unit and pump that provide roughly 10 to 25 gallons per hour per watt (or less for units not operating at peak efficiency).

So, youve investigated UV Sterilizers and just have to have one. How do you hook it up? Well, that depends on your set-up. If you already use a canister filter, you can install it in the return line. Be sure to choose one that will provide the recommended 10 to 25 gallons per hour per watt as described above (and at:

If you dont use a canister filter, you will have to purchase a pump or powerhead to run the UV. You can use a submersible pump and connect the outlet to the UV unit which will either hang on the tank or be installed beneath the tank in the stand, or you can use a siphon to get the water to the UV unit and then pump it back to the tank via a spray bar.

The UV unit is usually installed after the filter, but in searching for information for this article, Ive found that this may not be the best idea. Ill let you decide. Heres a site I found that suggests just the opposite:

Some pond people insist that you connect the UV after the water has gone through the filter system. They state the clean water now passes over the bulb and it kills the algae. They are 100% right. But where in the heck did the dead algae go. Was it zapped into outer space? Not hardly! It ends right back in your pond to become a food source for the existing algae.

Having read that article, I would now recommend that the UV be installed after the filter (to provide clean water to the UV) and a mechanical filter be installed after the UV unit to trap all of the dead algae and stuff that is killed by the UV sterilizer. This would provide the best protection against waterborne disease organisms, bacteria and algae without sending all of the dead organisms back into the tank.

In summary, if you have a central system (as in a fish room), a salt water tank, delicate fish or just want the added peace of mind, UV may just be for you.

If you have a reef tank, shut down the UV during feeding time.

Size the system correctly to provide more than 1 second of dwell time.

Always shut down the UV when medicating and doing maintenance.

DONT look into the light!
Post InfoPosted 26-Jan-2006 11:18Profile Homepage Yahoo PM Edit Report 
Big Fish
Posts: 479
Kudos: 991
Votes: 10
Registered: 25-Sep-2003
female australia

That is brilliant, it has answered all the questions that I have had over UV's, you did a fantastic job.

Post InfoPosted 26-Jan-2006 11:18Profile PM Edit Delete Report 
Small Fry
Posts: 5
Kudos: 5
Votes: 0
Registered: 17-Mar-2004
Excellent! Might have to try one someday.. What kind of price range are we talking about for a sterilizer?

Post InfoPosted 26-Jan-2006 11:18Profile PM Edit Delete Report 
Fish Master
Posts: 1515
Kudos: 2354
Votes: 4
Registered: 09-May-2003
male usa
UV Sterilizers range from around $70-200 US dollars. A 9 watt is good for tanks up to about 150 gallons though so you can get a decent one in the lower price ranges.
Post InfoPosted 26-Jan-2006 11:18Profile Homepage Yahoo PM Edit Delete Report 
Ultimate Fish Guru
Posts: 4241
Kudos: 1074
Registered: 04-Nov-2003
male usa
EditedEdited by tetratech
Thanks Techjak, Nice job

I use a 9watt on my 72gallon S.A. tank and I can't imagine life without one. Not only did it destroy a green water problem I was having but my cardinal tetras are doing great because it's destroying pathogens that often affect these sensitive fish.

My Scapes
Post InfoPosted 15-Feb-2006 04:09Profile PM Edit Delete Report 
Posts: 58
Kudos: 25
Votes: 18
Registered: 30-Jan-2005
I've seen UV's go for over 300 USD... but never $70?
Post InfoPosted 08-Jun-2006 03:08Profile PM Edit Delete Report 
Fish Guru
Posts: 2563
Kudos: 571
Votes: 12
Registered: 17-Sep-2002
female uk
They are also great for fishkeepers in countries where a smaller range of medication is available.

For example, in the UK, antibiotics are only available on prescription (from a vet or doctor) and therefore are almost unobtainable to the hobby fishkeeper. I have found that using my UV during an outbreak of disease helps prevent secondary infections and in some cases, reduce the impact of the primary infection.

I like to think that whoever designed marine life was thinking of it as basically an entertainment medium. That would explain some of the things down there, some of the unearthly biological contraptions
Post InfoPosted 14-Nov-2006 01:30Profile MSN PM Edit Delete Report 
Small Fry
Posts: 4
Kudos: 3
Votes: 0
Registered: 13-Jan-2007
male australia
EditedEdited by BGKF1
techjak Wrote:
All you ever wanted to know about UV Sterilizers

Good information, however I would recommend that you note/add that if fish are in a UV Sterilised tank and are then transferred to a non-UV Sterilised tank they are often much more susceptible to diseases. I also wouldn't recommend operating an UV Steriliser continuously.
Post InfoPosted 14-Jan-2007 04:18Profile PM Edit Delete Report 
Small Fry
Posts: 2
Kudos: 0
Registered: 14-Jun-2006
male usa
been using a uv now for6 months done away with floating alge and my tank is crstal clear
Post InfoPosted 22-Jan-2007 22:32Profile PM Edit Delete Report 
DeletedPosted 16-Feb-2007 01:35
This post has been deleted
Small Fry
Posts: 2
Kudos: 0
Votes: 1
Registered: 15-Feb-2007
Nice description!

I was wondering, though, on how to remove the copper before running the UV light. I guess the usual carbon thang shoud work!

But you are right, as running the UV light while treating with copper is a no-no.
The copper that is many, if not all of the medications today, is a form called chelated copper, which means that the copper is stable and will not react in the toxic way that pure copper will in water. When it is stable, it means that they have added a substance, possibly a salt, so that the valence electron shell is fully occupied. Voila! No reactions! The salt is also added for the "delayed-medication" effect. The bonds are not that strong, so that time and substances in aquarium water will break the bonds and release the medication.
When you run the UV light, there is enough energy in the UV light to break apart the bonds of the copper. When the bonds are broken, you get unwanted salt, as well as toxic copper.

Anyways, nice description techjak! /:'
Post InfoPosted 16-Feb-2007 01:35Profile Homepage PM Edit Delete Report 
Fish Addict
Addiction Hurts!!
Posts: 542
Kudos: 330
Votes: 355
Registered: 28-May-2007
male usa
I've been messing with some stubborn Ich in my 20 gal FW tank. Will and UV Stabilizer work in my tank or is it only for SW?

Post InfoPosted 23-Jun-2007 04:07Profile PM Edit Delete Report 
Posts: 5108
Kudos: 5263
Votes: 1690
Registered: 28-Dec-2002
male usa us-colorado
Hi Scott,
Yes, a UV sterilizer will work in either salt or fresh
water. It will only kill something that is drawn into
it and it will only kill the Ich parasite while it is
in the free swimming stage of its life. Otherwise it
is down between the grains of gravel or stuck to a
You would need to increase the temperature of the tank,
to speed up the life cycle, and run the UV constantly
to achieve your goal.

Actually the best cures are the ones with copper or
formaldehyde in them. Again, increase the temperature
and dose the tank as directed.
If you are reinfecting the fish and just cannot seem to
be rid of the parasite, you need to look at
your housekeeping techniques.
Are you using the same net(s), are you using something
between tanks, are you sterilizing everything between

In the pet shop, we used to keep several nets soaking in
water treated with Ich medication. When we needed a net
we would take one out of the bucket, rinse it off and use
it. We would never use the same net between tanks. If
we were catching fish from more than one tank, we would
catch the first one(s) return the net to the bucket, and
take out another.


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--
Post InfoPosted 23-Jun-2007 08:19Profile PM Edit Delete Report 
Posts: 52
Kudos: 25
Votes: 6
Registered: 27-Jan-2007
One of these would be the safest way to get rid of disease causing organisms.

17 years experience with freshwater.
Post InfoPosted 07-Jan-2008 07:18Profile PM Edit Delete Report 
DeletedPosted 20-Jun-2009 05:57
This post has been deleted
Post Reply  New Topic
Jump to: 

The views expressed on this page are the implied opinions of their respective authors.
Under no circumstances do the comments on this page represent the opinions of the staff of Forums, version 11.0
Mazeguy Smilies