Tropical Fish Keeping - Aquarium fish care and resources

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-   -   UV Sterilisers, what do they do? - Do they effect your Filters Bacteria? (

Dawes 11-09-2012 05:57 PM

UV Sterilisers, what do they do? - Do they effect your Filters Bacteria?
I've been noticing that alot of the high-end external filtration systems have UV Filters in them, and I was curious as to what they do to the Aquarium, and how they effect the bacteria in your Filter, as I have heard the UV kills off everything and anything that is microscopic and biological, but I cant see that being the case as it would contradict the point of having a Filter, both internal and external.

I've also known people to use Internal Filters and then later on buy a separate Internal UV Filter to work along side their current, Internal 'normal' filter.
- I take it this would be just as good as having a built in UV light in an external filter?(Apart from quality differences).

If anyone could tell me the pros and cons of these, as I've always wanted to know and it is quite hard to get a definitive answer just by searching and looking around.

- Thanks!

AbbeysDad 11-09-2012 08:16 PM

The UV sterilizer kills algae and water borne pathogens. The beneficial bacteria we culture attaches to hardscape and is not free floating. Still, a UV sterilizer should only be installed in an established tank as it could inhibit BB development in a startup tank.

Although some are sold on UV sterilizers, they are not really necessary anymore than a diatom filter is 'necessary'. However, they do offer their specialized advantages.

Byron 11-10-2012 02:49 PM

I agree. This is a costly bit of equipment that is not necessary, or should not be, and may do more harm than good, depending.

nickt30 11-10-2012 08:02 PM

uv sterilizer used on water preconditioning tank
i have a 15gal tank that i use to pretreat the water before water changes. I add the tap water conditioner and pre heat the water. It is located on a 6.5ft hutch so i can just gravity feed water to my tanks. After a while i was getting some really funky growth in this tank. I added a small HOB filter to keep things moving and i added a uv sterilizer. This really cleaned up the water so it is ready anytime i need to do a water change or top off a tank. I do notice that the water got extremely clear when i placed it in. I used to use 254nm uv light at work and they are dangerous and a stong sterilizer. other then that use i have not seen any research to clearly suggest the benifit of it in a cycled & populated tank.

AbbeysDad 11-11-2012 07:44 AM

Just a follow-up.
A UV Sterilizer can be a 'quick fix' for green water and excess algae problems. HOWEVER, most often it is analog-is to solving a problem externally, rather than addressing the root cause. By this I mean that there is some imbalance in the aquarium that fostered the condition that caused the unwanted life forms to proliferate. So the root cause of the problem is the excess light or nutrients or whatever. So the 'danger', for example, is that the algae may be killed, but the negative condition or water chemistry remains.

Byron 11-11-2012 11:30 AM

I admit that I know very little about UV sterilization, but fortuitously there just happens to be an article on this very subject in this month's TFH, authored by Valerio Zupo who is a professional lab technician who has written several scientific papers for international journals on the subject. The following information may give us a better understanding; what follows is direct citation or paraphrasing of the article.

UV radiation is dangerous to all living things, being able to cause mutations in DNA. UV rays contain a very high amount of energy and can penetrate cells, reaching the DNA where they cut the genome and undermine its functionality. After a few seconds, an auto-destruction program ("apoptosis") is normally initiated in the cell, At lower exposures, the cell may survive and simply be damaged.

All higher organisms (both plant and animal) are protected from low exposure to UV by their external structures (skin or cortex). Small organisms such as bacteria and protozoans lack these protective structures and can be very sensitive to UV radiation. UV rays themselves are quite delicate and can be blocked by filters such as some gasses (the ozone layer around the earth), glass, water, plastic, etc.

The effectiveness of UV sterilization is proportioned to its power and the amount of time of the exposure. The aquarium water must pass very close to the UV bulb and at specific speeds to allow for sterilization. The UV sterilization is done outside the aquarium since it will kill all bacteria and harm fish, invertebrates and plants.

In nature, there are no sterilizers. UV rays are filtered out before they reach the ground [this is why the thinning and depletion of the ozone layer is so critical]. Natural waters are not sterilized but they are perfectly clean. There is no reason to use sterilization in an aquarium in normal conditions, and most aquariums work perfectly in the absence of any sterilizing device. Aquariums that are overstocked or receive few water changes contain an increased concentration of bacteria that can be harmful. A UV sterilizer will lower the abundance of bacteria and other micro-organisms but only those in the water as it passes through the unit. Those that are scarcely mobile--attached to the substrate, wood, rock or plant leaves, on the fish or in its mucus--are not affected.

Both UV sterilizers and ozonizers [these are also discussed in the article] can be necessary, sometimes indispensable, to solve specific problems, but they should be used only when actually needed, with the right cautions, according to specific techniques.

pop 11-11-2012 01:09 PM

Our home water system has a uv sterilizer and I havenít noticed any ill effects but I have read that uv light is not helpful when cycling aquariums and since a cycled aquarium needs to be re-cycled every time the ammonia and nitrate, nitrite concentration is altered I donít think using uv light would be very helpful. I donít think uv light has much effect on the water column after the water has passed the light.


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