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

 

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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!

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.

Reference:
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!!!

NEXT, COLD CATHODE LAMPS:
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

For a graph that shows HOW LITTLE UVC ENERGY IS PRODUCED BY THESE COLD CATHODE UV BULBS THAT ARE NOW COMMONLY SOLD!

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
*http://en.wikipedia.org/wiki/Fluorescent_lamp
*http://en.wikipedia.org/wiki/Hot_cathode

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; Steps to a Healthy Aquarium & Sick Fish

Aquarium UV Sterilizers; Misinformation

Updated 7/8/23 (Original Article, April of 2007)

I continue to follow the threads on forums, aquarium articles, and blogs about UV Sterilization.
It still amazes me how much misinformation is spread about this, some masked in science. As I have stated many times before, a UV Sterilizer is not essential for any aquarium, however even for goldfish I have maintained tanks with true UVs, and many other variables, I have noted a differences because of the sterilizer (especially Category A UVs such as the TMC/AAP Vecton UV Sterilizers). Many times this has lead me to a thriving tanks.
For a better aquarium forum: Everything Aquatic, Aquarium Forum, pros that care

What I also find interesting, is that many of these same persons who trash UVs, will then state a protein skimmer as essential.
I have maintained tanks with and without Skimmers (again every other possible variable the same or as close as possible), and noted the changes in measurable parameters and found that yes they are useful, however often not by much and that Mud Filters, DIY DSB filters or similar can often replace them.

Now admittedly Protein Skimmer have come a long ways since I started in this business over in the late 1970s with vastly improved, more efficient, and with less hassles Protein Skimmer such as the TMC V2 Skim Protein Skimmers and similar high end skimmers.
My point is not to trash Protein Skimmers (which have improved), but to only point out the hypocrisy of many in the marine keeping hobby that will insist on a Protein Skimmer while trashing a UV Sterilizer, despite the science behind their use.

Back to the subject at hand, here is a thread I will comment on.
In this thread one person who offered proof (albeit not of the perfect scientific nature, but as good as it can often be within this hobby) was attacked dog pile style without other backing up their statements other than criticizing his methods:

Author #1:

“If you read some scientific documents about UV sterilization of water you will know they talk usually about a standard long, 40W mercury UV tube in a 3" diameter lamp and water passing at the speed about 500 gph or less. This kind of setup delivers dosage of about 18,000 mW-sec/cm2. In order to increase this dosage you need to lower the water flow.
For example, 250 gph flow will in above mentioned lamp would be exposed to the almost double dosage of 34,000 mW-sec/cm2. This dosage is enough to kill bacteria, yeast, some mold spores, viruses and microalgae. And some aquarium grade lamps achieve this effect with unicellular algea.
To kill protozoa (like a well known from school "Paramecium" or our ich-causing "Cryptocaryon irritans") you would have to increase the dosage to the range of 200,000 mW-sec/cm2 !!!!!
This would mean that if you had 3" diameter lab-grade UV lamp with a 40W mercury tube you could give it maximum water flow of 40 gph... How about that!”

My Comment:

First, most studies I have read show under 10,000 mW per se/cm2 for bacteria. (References below)

Second, I have read articles that have shown 30,000 + mW-sec/cm2 with 90 watt bulbs at a rate of 200 + gallons per MINUTE (which even I find hard to believe). My point is it often depends on whose data you look at.

Third, there is more to treatment of Cryptocaryon than just out-right sterilization (I would not want it that high in my reef tanks!!!), there is also the Redox potential which Sterilizers improve and also general over all water quality that is aided by the addition of an Ultraviolet Sterilizer.
Finally, each unit is different and there are many variables from age of the bulb (even a 3 month old bulb has lost 25%), to temperature, design of the unit, pre-filtration, and to flow rate which I have found to be best at 20 gph (or less for most good units in aquarium applications).
See: Filter Max Pre-Filters

References:

• UV Disinfection
• Triangular Wave
• UV sterilization

Author #2 (edited):
I started keeping marine fish in 1975. I first added a UV sterilizer to my tank about 1977 or '78. It was an 8 watt unit. In the early '90s, I added another. In 2005, I went back to an 8 watt unit.

Without a hospital tank, adding a new fish was always hazardous.
Back when I had no UV on the tank, once one of the fish started showing signs, the life expectancy of that fish was usually less than 3 days; they could not take the combined stress of the parasites and the copper treatment. Other fish in the tank would invariably show signs of infestation later, but would usually make it through.

Once the first sterilizer was added, the rate at which the disease spread decreased; my theory is that some of the parasites were being killed in their free-swimming stage.
After that, the first fish to show signs usually survived, and some of the other fish would never show any signs at all. Once I added the second sterilizer, I never lost a fish to Ich, though I did get the occasional infestation.
In short, there was a direct relationship to the number of watts of UV and the intensity and rate of spread of the disease.

Since I was not religious in changing the UV Bulbs (and the bulbs get less effective with time), I was also in a position to notice that an outbreak was worse when the sterilizer bulb was pretty old. Again, this didn't happen once I had two units running.
Here is a source for premium highest UVC output bulbs: Aquarium/Pond UVC Replacement Lamps

My Comment:

This person most likely had decent units with low flow rates, pre filtration, and useful discernment.
Without elaborating too much (my expanded articles have much about this), as stated earlier there are other aspects of UV Sterilizers such Redox Potential, this is not a hard test to perform; simply test the Redox without a UV and then run one for a week and test again, easy!
So many who trash persons like this have not considered all the variables if they have failed, myself I have seen UV Sterilizers not do a damn thing. These were often 8 watt units running off a sump with a flow rate of 800 gph, a calcified quartz sleeve and poor pre filtration. This is not to say a 8 watt unit (or less) cannot work, just not under those conditions.

• The "15 Watt Custom UV Sterilizer" I made has performed well in most every application I have placed it in.
• The standard TMC Vecton & Titan UV Sterilizer are the best when all types are considered, especially the ultra premium TMC Titan UV, which is far superior to every other brand at any price point when compared apples to apples.

What a UV Sterilizer is, is a tool for good aquarium husbandry along with water changes, filtration, protein skimmers and more. In many of my side by side applications with and without, the UV was just one more piece of the puzzle to improved water quality in let’s face it, an artificial environment (unless we want to kid ourselves).

I can think of one experiment in particular with several goldfish tanks at a large service customer of mine. All these tanks in particular had canister filters, cleaning and the same feeding schedule and bio load; the only difference was UV Sterilizers.
The difference in amount of diseased goldfish, growth and color was very noticeable (the vice president did not kno we were performing this experiment and even commented about why some tanks did better than others, after which she had us install UV Sterilizers on all).

Copyright; Carl Strohmeyer

Please read this article about UV Sterilization for a MUCH more in depth understanding of How a UV Sterilizer Truly works:

ULTRAVIOLET STERILIZATION (How it Works)