UV clarifiers in your pond
UV Clarifiers and UV Sterilizers.

UV clarifiers and UV sterilizers: Terms that are commonly heard in the world of ponds and water gardening and sometimes are surrounded by a veil of mystery and disapproval.

If you ask some people they might say they are bad, you ask some others and they might say that they are good. Who is right? In fact they are both correct. A lot of people think they do the same thing but this is far from correct. Technically, UV clarifiers and UV sterilizers are the same as in they both contain all of the same parts, but where they differ is what they are used for.

How Do They Work

Since UV clarifiers and sterilizers are made from the same parts, let’s look into how they work. Both units do their job using a high output ultra violet bulb that is protected by a crystal sleeve. These bulbs are designed to emit light (energy) waves that are out of the spectrum of visible light.

So what’s this mean? The particular wavelength of light that the bulb emits is harmful when coming in contact with things around it. So when organisms such as bacteria, parasitic protozoa, and algae cells come in contact with the light from the bulb, their DNA is altered, ultimately causing death to the organism. In fact, they are “nuked.”

Bacteria and algae are sensitive to UV light, and a short exposure is all it takes to “nuke” them. This would be a good job for a UV clarifier. Parasitic protozoa, like ich and costia, require a longer exposure time so the water would need to flow more slowly through the UV light, so a sterilizer is needed.

The longer the organism is exposed to the UV light, the more damage is done and that’s where the main difference between clarifiers and sterilizers lies – how quickly the water flows past the bulb, or how long the water and the organisms are exposed to the light.

Now let’s talk about things that affect the efficiency of the bulb. Generally speaking, although the bulb may still emit light, it is only effective at killing algae for around 12 months. The cleanliness of the water and of the crystal sleeve also influence the effectiveness of the bulb – the dirtier the water and sleeve, the less the UV light will be able to come into contact with the nuisance organisms. To prevent sludge and lime build up, the sleeve can be cleaned with a mild detergent, followed by a rinse of clean water.

Sterilizer vs. Clarifier

UV Clarifier

We all hate that dreaded algae bloom in our ponds. If you own a water garden then you know your worst enemy is the unsightly green water.

A well-balanced pond ecosystem rarely has a problem with green water, but any water feature, when out of balance, might require you to resort to artificial means to control algae blooms. This is where UV clarifiers come in handy. Their main purpose is to clear the water and get rid of those nasty algae blooms that cause green water. But remember, UV clarifiers only get rid of the single-celled, floating algae. It does not get rid of other forms of algae such as string or blanket algae.

UV Sterilizers

Sterilizers, on the other hand, do exactly that. They sterilize. Commonly used in the aquarium industry and fish husbandry as another line of defense in preventing major parasite and bacteria outbreaks, they are designed to get rid of and kill just about everything in the pond water. To accomplish this, they need to have a longer contact time with the water. Sterilizers require extremely slow flow rates compared to clarifiers. So, if you want to make sure you zap everything in your pond, then this is the way to go.

You should also be aware that UV sterilizers cannot be used with certain medication applications because in addition to the effect it has on bacteria and parasites, it can have a similar effect on the makeup of certain medications, often times rendering them useless. So a good rule of thumb is that the sterilizer be removed or turned off when medicating.

Where do these fit with the general hobbyist? A lot of hobbyists use sterilizers on a smaller scale, in the 9 to 24 watt range, in their own quarantine tanks. Whether you choose a UV clarifier or sterilizer, it should be installed in-line after the skimmer or other mechanical filter, pre-filtering the water to keep the unit from coming in contact with heavy debris.

A Place in the Hobby

When your shopping for a UV clarifier or sterilizer, you need to know two things to help you decide which unit is best for your pond – what is the water volume of your pond and what do you expect the UV to accomplish? Sterilizers and clarifiers definitely have a place in the hobby, but they are only helpful when used in the correct application. Knowing when and how to use them can save you from a lot of headaches and let downs that result from improper use.