. Aquarium and Pond UV Sterilizer, Clarifier Reviews; Problems

UV Sterilizer Reviews; Information Articles, Ideas, Comments, and Links to even more Resources about how UVC Sterilization works in Aquariums/ Ponds

aquarium and pond UV posts, information, articles, resources, blogs

Information Articles (Posts), Ideas, Comments, & Links to even more Information about how UV (UVC) Sterilization works in Aquariums/ Ponds.
For a COMPLETE up to date article about aquarium and pond uv sterilization, please visit this site:
UV Sterilization in Aquariums and Ponds; How it works

For all Articles, from basic to advanced, such as UVC, Watts, mW/cm2, please scroll down the Right Side Bar of this site for easy links

9 Watt UV Bulb; Aquarium & Pond Germicidal, Review


Updated 12-25-18

What's in a UVC Replacement Bulb?

If you have followed this blog/website for some time, you would know that ONLY a 254 nm HOT CATHODE LOW PRESSURE UV Bulb should EVER be used in your Aquarium UV Sterilizer, Pond UV Sterilizer/Clarifier, or Air UVC Purifier.

*Hot Cathode vs. Cold Cathode UV Bulb; Are these worth purchasing?
*Actual UV-C Emission from a UV Bulb; Aquarium or Pond

This is not to say that these higher output high quality UV Bulbs/Lamps are not easy to find, as they can be found. But not for prices much under $14-$15 and certainly not for $5.99 as some eBay sellers such as "Discount Aquatic" who have used ("copy & pasted") without permission information from premium UV bulb seller AAPs web page that implies their UV bulb is the same! BEWARE, a close observation shows the UV lamp/bulb these and other sellers is NOT THE SAME! Why spend the money on a UV Sterilizer only to put in a $5.99 blue light bulb??

Several manufacturers such as American Aquarium, Purely, & Phillips all sell ONLY hot cathode, low pressure 254 nm UV Bulbs that are also include the patented heat reducing technology or Norman lamps high efficiency, low heat/HO technology.

Supplier of these bulbs: American Aquarium Products; UV Bulbs

Please Read the full article to understand the difference between many of the 9 Watt UV Replacement Bulbs sold

Unfortunately though, MANY if not most of the low cost UV Bulbs sold on eBay (such as the Jebao Brand commonly sold on eBay), Amazon (under the brand 'AnyRay'), Nextag under brand names such as Ocious are NOT these same low pressure, hot cathode UV Bulbs intended for level one UVC Sterilization in pond or aquarium applications, RATHER these are medium pressure UV lamps INTENDED AS NAIL CURING LAMPS with a UV efficiency of only 7%!!
I am not necessarily accusing these sellers of fraud, rather most of these sellers find a source for the 'nail curing UV bulbs' and outwardly these look almost the same, but for a lower cost, so they see an opportunity to get a UV bulb for a lower price that they can in turn market at a lower price. Unfortunately most of these sellers would not know the difference between a low pressure UV bulb and a medium pressure UV bulb (again the later is only generally intended as a nail curing UV bulb).

See References:
UV Lamps, Bulb; How they work
Actual UV-C Emission from a UV Bulb; Aquarium or Pond

Actual UV Output in Lamps purchased from Amazon

Quite bluntly these medium pressure nail curing 9 watt UV bulbs at 7% germicidal UVC irradiation simply CANNOT destroy the bacteria or maintain aquatic Redox at any useful/normal flow rate when compared to the high UVC output hot cathode UV-C Bulbs!
A source for these bulbs:
True Level One, Low Pressure UV Bulbs for Aquarium or Pond Use

Now to the title of this article/review;
Those purchasing a replacement 9 Watt UV Bulb will find this UV lamp to be one of the most common UV Bulbs sold incorrectly as replacements when in fact many are not for aquarium, pond, purifier use, despite advertising to the contrary!

Many of these are simply are NOT going to do the job.
These cheap 9 Watt UV Bulbs (often sold for under $10) are only useful for nail curing or similar, NOT to attempt to maintain Level 1 Sterilization in your important Aquarium or Pond UV Sterilizer!

Please Reference: Aquarium/Pond UV Sterilization
A source for good to premium UV Sterilizers: UV Sterilizer!!

What is also noteworthy, although often difficult to find, is some 9 Watt G23UV Replacement Bulbs use patented methods to lower operating temperature which increases the efficiency and UVC output.
Such as:
  • Patented Heat Reducing Technology
  • Norman lamps super high efficiency HO/low heat UV Bulbs.

Put in simple terms this makes for:
  • Lower operating temperatures which in turn increases energy directed as UVC (which is why you have a UV light in the first place). This 5° C difference increases efficiency about 5% or more, adding to the 75% improvement of these low pressure UV lamps over common lower cost medium pressure UV lamps/bulbs sold at online discounters and home improvement warehouses.
  • Longer Life and higher output over the life of the lamp.
  • Easier starts, which new hot cathode UV lamps are often difficult to start initially.

Now look and see if your bargain Amazon, eBay, etc. UV Bulb has this heat reducing technology;
Likely not!

THE FACTS ARE; the direct wholesale cost in volume purchasing is more than $10 for TRUE Low Pressure, Hot Cathode UVC Replacement Bulb/Lamp, so how is some Vendor going to sell these for much under $14 and pay the eBay seller fees, Amazon Fees, etc. (often offering shipping at below actual cost too), and still make a profit??
Of course the simple answer, which is not rocket science, is THEY CANNOT! This is why it is impossible to get a CORRECT TRUE Low Pressure, Hot Cathode UVC Replacement Bulb/Lamp at the prices offered on many of these websites that advertise on Google, etc.


9 Watt UV-C Bulb Comparison, eBay, Jebao, etc versus quality lamp

Another UV bulb that commonly comes up in search and is sold as less expensive alternative is the 18 Watt UV bulb/Lamp which it too is often a low output medium pressure UV Bulb with less than 7% UVC output.
This is another instance one should be careful of picking the first UV Bulb that comes up in Google search and instead choose a true low pressure hot cathode.
See my article/review for this bulb here: 18 Watt UV Bulb Review
Or to purchase a true 18 watt uvc bulb; True level one UVC capable 18 Watt UV Bulb

Simply put do NOT let Google, Bing, Yahoo guide you to one of these many websites selling these mostly useless UV Bulbs that produce little UVC necessary for an effective UV Sterilizer or Purifier.
Spend a little more and purchase a American Aquarium, Purely, or Phillips 9 Watt Bulb, which often still only sell for $14 to $25 online.

American Aquarium Products hot cathode 9 Watt is sold near cost as a promotional item and is THE true hot cathode, low pressure 9 Watt UV Bulb to purchase for both quality & price!!
See: 9 Watt UV Bulb

Please also read this article:
UV Lamps, Bulbs; How they work, Coatings, more

The bottom line is while you can certainly get a good deal for a good UV-C lamp/bulb, the old axiom still applies "THAT YOU GET WHAT YOU PAY FOR"!!

Finally, if you are having issues with your UV Bulb or Ballast or you would like some more information to understand why most 9 Watt UV Bulbs now sold are sub par, PLEASE give the video below a full viewing:

UV Bulb Review, Troubleshooting Video

Please reference this unique, in depth, & researched article that is IMPERATIVE READING for anyone interested in moving from basic aquarium or pond keeping to more advanced aquarium or pond keeping:

UV-C Sterilization Use; Beginner to Advanced

If you are looking for the optimum, MOST EFFICIENT LED lighting for your aquarium, look no further than the 5 year warranted AAP AquaRay line of LED lights (beware of a parasite retailer selling out of their home that Google's poor search algorithm brings up), please follow this link if you want the genuine AAP AquaRay:
AquaRay LED Lighting

By Steven Wright with input from Carl Strohmeyer-PAMR

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Hot Cathode vs. Cold Cathode UV Bulb; Are Long Life, Easy Start UV Bulbs worth purchasing?


UV-C Hot Cathode Quartz Germicidal Lights/Bulbs

Long Life, Easy Start UV Bulbs; Are Cold Cathode, Low Output UV Lamps worth purchasing?
UV-C Bulb Problems

Updated 10/15/2020

First a little background information:

UV-C Hot Cathode Quartz Germicidal Lights/Bulbs are similar in their operation to the standard fluorescent lamps. The Hot Cathode lamp operates from a ballast or transformer and requires a device such as the glow bulb starter or electronic ballast to preheat the electrodes in order to start the lamp.

The electrodes, located at the ends of the lamp, are tungsten filaments coated with emission material and, under normal operation, govern the life of the lamp itself (not output).
Operation at low temperatures as found in many ponds in the Winter or early Spring may result in excessive lamp blackening and more rapid depreciation in ultraviolet output. As well, starting of the Hot Cathode lamps at low temperature may require a few minutes.
It is also noteworthy that the tungsten filament used in the High Output UV-C Hot Cathode Quartz Germicidal versus many cold cathode are more fragile and burn out more quickly, especially with many "starts".

Some high end Compact Hot Cathode Germicidal Lights/Bulbs such as those made for/by "American Aquarium" UV; G23, G11 have small metal pre-heat elements that aid in starting and reduce cold start times and wear and tear on the filament.

American Aquarium Lamp Resource: American Aquarium Products Compact UV Bulbs

Because of the voltage surge required by a Hot Cathode UV-C Bulb to light, ANY electronic ballast that is not providing this voltage due to age, damage, or simply poor quality, WILL fail to light a new Hot Cathode while this same ballast can still light an older hot cathode or a new cold cathode.

Hot cathodes generally achieve much higher power density than cold cathodes lamps and therefore produce more energy per given watt of energy used, making these a more desirable type of UV Bulb/Lamp for this reason alone.

Despite the shorter life, and requirement for optimum functioning ballast to light aside; these UV lamps produce an optimum UV-C at 254nm, which is what you need for proper sterilization!

smartpond 700-GPH Submersible Pump cold cathode UV bulb, lamp
Some manufacturers/retailers in an attempt to lure customers into thinking a cold cathode bulb is a the way to go just because of the longer lifespan are now incorporating these into UV pumps.
This Smartpond 700 gph not only utilizes these poor UVC emission UV bulb/lamps, they use a 2.5 watt bulb that even if the optimum low pressure, hot cathode UV lamp were used, it would fall far short of anything remotely effective as per the known science of UV Sterilization.
A Lowes web page even has some positive reviews for this product, but I can assure you that this is clearly the placebo effect as there is no way a 2.5 watt cold cathode UV lamp can provide any real results.

Similarly many products made in China are made to differing specifications depending upon what the retailer/distributor desires as a "price point".
This is VERY common with SunSun products where UV Sterilizers as well as canister aquarium and pond filters will come with ballasts only meant to fire low output UV bulbs/lamps. So when the owner purchases a higher output true UVC lamp, the bulb may not fire or burn out in short order due to difficulties firing these UV lamps.

UV Sterilizer Use, Facts & Information based on Experience and Research

As an example from the above referenced article, an optimal hot cathode low pressure 2.5 watt UV lamp would only provide Sterilization at 75 gph and true algae control at 125 gph. But this product does not even use this lamp and also has a poor flow pattern and less than optimal distance from the UV lamp inside the Sterilization chamber.
So a pump rated at 750 gph with this UV bulb/lamp is basically a pump with a pretty blue light decoration inside- DO NOT PURCHASE!!!

Cold cathode lamps have no thermionic emission coating to wear out and can have much longer lives than hot cathode thermionic emission tubes, however cold cathode lamps are less efficient than Hot Cathode lamps lamps because the cathode fall voltage is much higher (See Resources).

Many sellers of these lower price, longer life, cold cathode UV bulbs, claim these bulbs will provide longer life & easy/quick lamp starts often at a much lower price. Often these are sold at eBay and many "Top Bulb" or "Ushio" sellers that come up on Google's spammy algorithm.
What many of these sellers may not even realize (many probably do and choose to market these bulbs falsely), is that most of these bulbs are only actually intended as nail curing UV bulbs, NOT for use in true level one UV Sterilizers for pond or aquarium use!!

While this is true, these lamps/bulbs produce UV-C irradiation that can be as low as 185nm (which produces undesirable ozone) and as high as 330nm (which is UVB, not UVC).
With as little as 7% desirable UVC with these cold cathode, medium pressure UV bulbs; How is saving a few dollars and getting a few extra months life worth a bulb that is almost useless compared to a vastly superior Hot Cathode low pressure full UVC Bulb????

Obviously I am providing generalizations since these lights can vary, but what is clear is you are not achieving the optimum UV-C at 254nm.
As well, advertising 8000-10,000 hours of life is another dead giveaway that the lamp is NOT a High Output, Low Pressure Mercury Lamp since closer to 4000 hours is all you should expect for peak performance.
See:UV (UVC) Lamps/Bulbs used in Aquariums/Ponds and How they Work


Sadly many buyers are impressed by the "easy starts" and "low price" that these cold cathode UV Bulbs provide and the fact that these long life/low output UV Bulbs will often light in UV Sterilizers with worn ballasts that do not have the energy (voltage surge) to fire/start a new Hot Cathode Germicidal UV-C lamp/bulb.

Add to this problem that many UV Sterilizer ballasts degrade quickly (especially when used for ponds where more moisture is present) resulting in the un-informed user believing that their low end UV bulb is actually better than a a premium UV-C Hot Cathode Quartz Germicidal Light/Bulb when the OPPOSITE is the truth!
Even popular UV Sterilizers such as the over rated Turbo Twist has a high ballast degradation rate.

See: Potential UV Sterilizer Problems; Weak or Poor Quality Ballasts.

Purchasing a High Output 254nm UV-C Hot Cathode Germicidal Bulb for a UV with a weak/degraded ballast that will not light/fire a high output bulb, then purchasing a low output long life bulb that does work with this weak ballast is not an indicator of bulb quality, rather a lack of understanding of what makes a TRUE UVC producing lamp!!!

UV Bulb Resource: High Output Germicidal Bulbs

Unfortunately many manufacturers now even sell these almost useless for UVC sterilization cold cathode UV bulbs. As these will almost always light, and this allows for UV Sterilizers with a poor ballast designs that do not last long to appear to be functioning.
Worse yet, I have had customers/clients forward emails/letter claiming only their "original equipment" UV replacement bulbs should be used as their UV Sterilizers may not light the vastly superior hot cathode UV Bulbs.

The result, if a potential customer falls for this incorrect line of reasoning, is a UV Sterilizer that is almost a useless device as it is producing a fraction of the necessary UVC energy for level one or two sterilization or even clarification!
This is putting the blame in the wrong place, keeping a UV Sterilizer with a ballast that has degraded and then only using cold cathode UV Bulbs makes no sense at all; why have a UV Sterilizer that is only 7-15% effective??

Such is the case with this sarcastic email:
"If many manufacturers are using easy start bulbs to make up for so called "weak ballasts" then why does the website (selling hot cathode UVC Bulbs) say hot cathode bulbs are compatible with their units? They clearly are not compatible with the majority of units."

The logic here totally escapes me!!

  • First this is not true, I am speaking about degraded ballasts, as even a new Coralife will fire a hot cathode "True" UV-C bulb, but a degraded electronic ballast will not.
    Using the Coralife again as an example, my aquarium maintenance business has serviced many of these over the last decade, with a high quality UV C lamp working fine, but once the ballast degrades, only a cold cathode or 'old' (mostly expired) hot cathode will fire (it is noteworthy that the life span of a Coralife ballast is lower than many UVs). The FACTS are that these ARE compatible with the majority of unit, assuming a fully functional, non degraded electronic ballast/transformer.

  • Second; Such a comment shows a total lack of understanding of fluorescent ballasts.
    A magnetic ballast would not have such a problem, since these utilize a fluorescent starter to provide correct "surge" voltage to light the UV-C Bulb.
    However most UV Sterilizers/Clarifiers utilize electronic ballasts of which many have poor circuitry that is easily degraded, especially by moisture; Once this happens a hot cathode true UVC Bulb cannot light.
    See: Weak of Poor Quality Ballasts

  • Third; the UV-C bulbs I have used and sold in my professional endeavors of aquarium/pond design and maintenance do and have worked in the majority of units

  • Forth; (and I will repeat myself), why would you want a UV Sterilizer that only makes a "pretty blue light" that is about 7-15% effective for UV Sterilization??

See also: Electronic UV Sterilizer Ballasts; Lamp Problems

The bottom line is do not be fooled either by the low price, long life claims, or ease of lighting (or lighting at all with a weak ballast) of these long life/easy start UV Bulbs, as these are not the reason you should be purchasing a replacement UV Bulb.
Your UV Sterilizer is meant for Sterilization (not a pretty "blue" light) and this will NOT be achieved with these low output UV bulbs (especially level 2 sterilization)!!

Unfortunately some manufactures utilize low output UV bulbs such as Hagen Laguna; these UV bulbs are very inferior to high output UV bulbs and the result is no Level One UV Sterilization and even poor Green Water control.

For further resources see these articles:

*UV Sterilization; Facts & Myths
*UV Bulb Troubleshooting Guide

For the Best Very Best UV Sterilizer for your Pond or Aquarium:

AAP Advantage & Vecton Premium UV Sterilizer

There is not any better UV Sterilizer for both durability and UV-C irradiation effectiveness than the AAP Advantage and Vecton UV Sterilizer line, at any price!

Further Reading of Interest:
Aquarium Disease Prevention
AQUARIUM DISEASE PREVENTION; Steps to a Healthy Aquarium & Sick Fish

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How UV Lamps, Bulbs Work; Low/Medium Pressure, Coatings


Updated 1/2/19

UV (UVC) Lamps (Bulbs) used in Aquariums and Ponds and how they work.

Recommended further reading:
Actual UV-C Emission from a UV Bulb; Aquarium or Pond

18 Watt G11 High Output UV Lamp This post is primarily dealing with UV bulbs(or lamps), that emit UVC radiation.
These UV lamps to be referenced here are used in the Aquarium/Pond Industry. I will discuss other UV bulb types as well, since these may someday show up in the Aquarium/pond Industry.

There are two common UVC emitting lamps types currently employed for pond or aquarium UV Sterilization: the low pressure and the medium pressure mercury lamp.

G4T8 Straight Tube High Output UV Lamp *The low pressure lamp emits its radiant energy between 250-260 NM which is where UV Sterilization is most effective with a UVC efficiency of about 38- 95%.
The emission peak of the Mercury electron transition within these low pressure (hot cathode) UV lamps is fixed in both energy and wavelength.

*The medium pressure lamp emits its radiant energy between 250 and 350 with many energy spikes in between (most notably around 320 which is more in the UVB range) with a UVC efficiency around 7-15%.

CAUTION: Many Medium-Pressure UV bulb/lamp manufacturers incorrectly boast that the broad UV spectral output of these lamps is more effective, which in reality is the exact opposite!!

low and medium pressure, uv bulb, lamp comparison

Best UV Sterilizer for aquarium, pond The low pressure lamp used by most all Premium Aquarium & Pond UV Sterilizers (not always the low end UVs such as Jebo & AquaTop) is clearly the better choice based on this information.
The low pressure lamp does have one flaw which the medium pressure lamp does not suffer from and that is the low pressure lamp is affected by water (or air) temperatures and operates best between 20 C (68 F) and 40 C (104 F).
Generally this is not a major concern considering most aquarists operate their aquariums well within this range. With ponds, this is still not a major concern in that most problems, including algae occur in warmer months. This problem can be also addressed with in-line heaters to pre-warm the water.

Many UV Sterilizers come with quartz sleeves which form an air pocket between the lamps and water that in theory increases operating temperatures.
HOWEVER my own tests have shown this improvement to be nominal at best especially when compared to a well designed direct contact UV Sterilizer.
In a test with a custom 15 Watt UV Sterilizer and a 13 Watt Quartz sleeve UV Sterilizer (a well designed one at that), the increase in temperate was only 2 degrees F (I have observed up to 5 degrees depending on the units compared).
This test started at 68 F and was conducted over 15 minutes, then water was removed from the units and the temperature measured. Unfortunately the quartz sleeve is accepted as a standard that sounds great in theory, but in practicality is not a significant improvement in most applications (I would recommend them in some applications such as Lobster tanks, but even here a pre-heater would also be recommended).

Please see references for which sterilizers used in this test:
Custom 15 Watt UV Sterilizer
13 Watt Quartz sleeve UV Sterilizer

Please see this article for much more about UV Sterilization:
ULTRAVIOLET STERILIZATION (How UV sterilization works)
This article explains the benefits and myths about aquarium and pond uv sterilization

Chemical Coating in UV Lamps/Bulbs

Chemical coating on UV Lamp, Bulb A few companies now provide a coating that they claim extend lamp output and lamp life. I have serious doubts to these claims based on the fact the emission peak of the Mercury electron transition is fixed in both energy and wavelength and I don't think coatings can emit additional UV to any advantage. Coatings usually capture UV and convert the emission wavelength via further energy transitions to some visible part of the spectrum, perhaps with several spectral peaks depending upon the composition of the coating.

One such company, Emperor Aquatics, makes the claim that their UV Lamps feature an internal chemical coating that provides added resistance to solarization.
This company uses a picture of a new bulb/lamp with the coating and a one without. HOWEVER I in my 30 + years have never witnessed the degradation shown in this picture, and I suspect that Emperor Aquatics is using an Ozone producing UV bulb/lamp to make their point.
I stand by my experience that these coatings are simply a gimmick to charge more for their proprietary UV Bulbs

UV Lamps/Bulbs Starting

Another aspect of UV lamps that should be noted is how they function or start. Most quality UV lamps commonly used are Hot Cathode (low pressure) UV lamps. The Hot Cathode Germicidal UV Lamps are similar in their operation to the standard fluorescent lamps.
The Hot Cathode lamp operates from a ballast or transformer and requires a device such as the glow switch starter to preheat the electrodes in order to start the lamp. The electrodes, located at the ends of the lamp, are tungsten filaments coated with emission material and, under normal operation, govern the life of the lamp. In view of the fact that the life of the electrodes is shortened by frequent starts, the lamp life is rated according to the number of times the lamp is started.

Operation at low temperatures may result in excessive lamp blackening and rapid depreciation in ultraviolet 'C' output.

See Also this related post:
Long Life, Easy Start UV Bulbs

*Aquarium/Pond UV Sterilizer Use
*UV Lamps & UVC Lamp Types
*UV-C Bulb Specifications; Aquarium and Pond

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