UV Clarifier and UV Sterilizer; What’s the difference?

UV Clarifiers & UV Sterilisers

People are often unsure of the difference between a UV clarifier and a UV steriliser. The general conception is that they do the same thing however there is a difference. Although UV clarifiers and UV sterilisers contain the same parts, the difference between them is more what they are used for.

Both units use a high output ultra violet bulb that is protected by a sleeve. These bulbs are designed to emit UV light to kill algae, bacteria and parasites.

Deciding which unit you require will depend on what you want for your pond. Generally, bacteria and algae particles are pretty sensitive to UV light, and a short exposure is all it takes to kill them. However, some parasites and bacteria like ich and costia, require a longer exposure time, as the longer the organism is exposed to the light the more damage is done to it.

Two main characteristics that differ between UV Clarifiers and UV Sterilisers are:

  • Wattage – Sterilisers generally have a higher wattage
  • Flow Rate – Sterilisers have a slower flow rate exposing the bacteria in the water to UV light for longer.

So, if your intention is to just clear up the pea green colour in your pond, without necessarily having a super sterile environment, then a UV clarifier is fit for purpose.

On the other hand, if you wanted to take it one step further and wanted to control viruses and bacteria in your pond, you will need a UV steriliser, which exposes the water to more UV than a clarifier.

Because of this difference in exposure, a steriliser will effectively function as a clarifier but large particles of waste can be pumped through the unit which gets trapped and causes the steriliser to be useless, a clarifier has a larger contact chamber and less restriction on solids passing through it trapping less of the large particles.

Factors to consider when deciding to purchase a UV steriliser or Clarifier:

  • Pond size – bigger ponds will need a bigger UV system.
  • The amount of fish in your pond
  • The amount of sunlight the pond receives – more sunlight causes algae to grow faster
  • Age of the lamp in existing steriliser or clarifier, most bulbs are effective for around 8 to 12 months
  • The cleanliness of the lamp and sleeve, sludge build up will prevent the UV light getting to the nuisance organisms.
  • Temperature of the water
  • If you have a lot of plants, then these will assist in the removal of nutrients, slowing algae growth.
  • Whether you already have a pump that you also intend to use for the UV light. Your choice of UV light may depend on the flow rate of the existing pump.

Sterilisers can help prevent spread of disease from one fish to another through the water. However, obviously the UV steriliser only affects organisms floating through the UV tube, so bacteria or parasites on the fish will not be affected.

Another important point to be aware of is to always shut off a UV for 24 hours when adding bacteria to your pond. A UV does not discriminate what it is killing so any beneficial bacteria added to your pond would likely pass through the UV and be killed off. Bacteria typically adheres itself to something (filter material) within 24 hours and is then safe.