Search for:


Aquarium UV Sterilizer; Common misinformation about using UVC in aquariums. - by Carl Strohmeyer

I continue to follow the threads on forums, aquarium articles, and blogs about UV Sterilization. It still amazes me much misinformation 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 had maintained tanks with as many variables (similarities) in place as possible and noted the differences and this includes thriving reef tanks.

What I also find interesting is that many of these same persons who trash them 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 (as well as UV Sterilizers and good over head lighting such as MH).

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 achive 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!”


First, most studies I have read show under 10,000 mW per se/cm2 for bacteria
. 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 often it 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 addirion 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 (a micron pre filter vastly improves sterilization), and to flow rate which I have found to be best at 20 gph (or less for most good units in aquarium applications).

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 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.


This person most likely had good 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 person 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 (and in the case a brand I will not mention, a poor mixing chamber design as well).

The TMC Vecton & Advantage well in most every application I have placed it in (The Terminator Compact UV Sterilizers do well too, one of the best compact UVs I have used).

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 of the company did not know 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).

For the further help with a basic understanding of using and maintaining a UV Sterilizer, please see this article:


Professional aquarium maintenance experience since 1978 as the owner of one of the larger aquarium maintenance companies in LA, CA.

I have been in the hobby since 1969.



       Article Source: http://www.ElectricArticles.com