UVC Pond Lamps - Everything you need to know

Adding a UVC to your Pond's Filtration system will help remove any green water caused by Algae or Blanket weed. Learn about the different types of UVC, and answers to your questions.

Article photo for UVC Pond Lamps - Everything you need to know
UVC Pond Lamps - Everything you need to know

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Every pond owner I know wants a pond that looks good enough to drink.  The water needs to be crystal clear, the fish need to be happy, birds need to be bathing themselves in your waterfall and your pond plants need to be flourishing.  

In all my years as a pond owner, I've always encountered the same problems.  Whether it be green mucky water, or blanketweed running rampant, Algae is the main cause of the problems and in this article I will go over why I use a UVC for my pond, what different types of UV lamps you can use and answer some of the most common questions related to UVC filtration.

What is a Pond UV Clarifier?

A UV Clarifier (UVC) is a Ultra Violet lamp that pond owners can add into their filtration system to help kill harmful bacteria, viruses and parasites (source) from their pond water.

The UV rays disrupt the DNA of microorganisms preventing them from reproducing and taking over your pond water.

Can you add any UV Light to a Pond?
You must ensure that any UVC is suitable for ponds and outdoor use.

How does a UV Clarifier help against Algae?

Algae is a living organism which once exposed to UV light will prevent the algae from breeding by disrupting it's reproductive cycle.  As the algae is no longer able to reproduce, your pond begins to become clearer and eventually the algae dies off.

What happens to dead Algae?
Dead Algae will fall to the bottom of the pond or be sucked up by your pond pump and trapped in your pond filter media.

Do I need a UVC to keep my pond water clear?

A UVC should be in addition to your existing pond pump and filter box.  Adding a UVC will not only ensure your water is clear from algae. In all my ponds, I've always used a UVC which I believe is the main reason my pond water remains clear all year round.

How long after fitting a Pond UVC will my pond start to clear?

Every pond is different, however a high quality UVC will show visible results within 5 days.  With a suitable pond pump and filtration system this will also help ensure any dead algae / blanketweed is filtered and removed from your main pond water.

Where is the best place to put a Pond UVC Filter?

The position of your UVC depends on the type of UVC filter you have (or thinking about adding).  I've listed below the different types of UVC solutions you can add to your pond - including a diagram of their placement.

Inline UVC Lamps

Inline UVC Lamp connects between the pump and the filter box
Inline UVC Lamp connects between the pump and the filter box

Inline UVC lamps are placed between your pond pump and your external filter box.  By choosing a separate Inline UVC, you are able to add to an already existing filtration system without the requirement to replace your entire filter box.

Pros of Inline UVC Lamps

  • Buy and size UVC lamp suitable
  • Easy to install
  • Modular - You can upgrade/replace at any time.

Cons of Inline UVC Lamps

  • Initial cost may be more when compared to all-in-one solutions
  • Can be quite time consuming to replace the bulb
For ponds which do suffer with excessive algae growth / blooms, you are not restricted to the filter box UV lamp wattage. For my own pond, I chose a much larger Inline UVC than what was required for my pond.

UVC Filter Boxes

UVC Filter Boxes have the UV lamp inside the filter box
UVC Filter Boxes have the UV lamp inside the filter box

UVC Filter Boxes are the complete solution.  The UVC is built into the filter box (located at the top) and whilst the water is filtering through the sponges it is subjected to the UV rays.

UVC Filter boxes are a great solution for new pond owners, or those looking to upgrade their entire filtration system.

Pros of UVC Filter Boxes

  • No need for additional pond pipe
  • Easy to replace bulb
  • Clean and Tidy

Cons of UVC Filter Boxes

  • If you want a higher wattage UVC, you require a larger UVC Filter Box
  • My own experience: I've had 2 UVC Filter boxes fail due to the seals around the UV lamp failing - this may be OK in newer models.

UVC Filter Pumps

UVC Filter Pumps - Submersible Pumps 

UVC Filter pumps, although not as popular as the other UVC solutions, feature the UV lamp within the pond pump itself.  Without any need for additional wiring or sockets, UVC Filter Pumps are pretty much the "all in one UVC solution".  Their small footprint does limit the size of the UV lamp which makes them unsuitable for larger ponds.

Pros of UVC Filter Pumps

  • All in one solution
  • Requires no extra wires to be connected
  • Suitable for Small Ponds

Cons of UVC Filter Pumps

  • Not suitable for larger garden ponds
  • Limited to small wattage UV Bulbs

Frequently Asked Questions about Pond UVC

I've prepared a list of frequently asked questions about Pond UVC's, their placements, common problems.  If you have a questions, please leave it in the comments below and I'll add your answer to this article.

Can you purchase a Solar Powered UVC?

Yes! New for 2023 - you can now install a Solar Powered UVC that runs for 2 hours per day. Read more.

Is UV light good for koi ponds?

UV light is great for all ponds (small and large) and certainly more useful in Koi ponds to help keep your water clear and kill any harmful parasites.

Is too much UV Light bad for a Pond?

UV Lights designed for ponds pose no threat to your pond fish or other aquatic life. I personally prefer to use a UVC that is rated for slightly larger ponds to control algae blooms.

Why is my pond still green with a UV Filter / UVC?

Allow up to 5 days for the UV light to break down algae (cause of green water). Also ensure that your filter media (sponges etc) are cleaned so they can clear dead algae from your water.

Should UV-C be before or after filter?

Pond UV-C should be placed after your pump, but before your filter boxes for the best results.

Do I turn my UVC off during Winter?

I personally don't, however I know many pond owners who do without any problems at all. Every pond is different, so try turning your UVC off and monitor your water quality.

What are the disadvantages of using a Pond UVC?

The only disadvantage is the increased electricity costs when running a high wattage UVC 24 hours a day.

Will UV get rid of Green Water?

Green water is caused by Algae particles. Whilst UV will break down the algae particles, you must also ensure that you have adequate filtration to them remove dead algae from your pond to ensure your green water is gone.

What happens if I turn my UVC off?

Turning off your UVC will allow algae (and other harmful bacteria/virus's) to reproduce and ultimately cause your pond to become green / cloudy and potentially harmful for your fish.

How do I know my UVC is working?

Most UVC's will have an inspection window. When the sun goes down check your inspection window for a blue/purple glow.

How often do I need to replace my UV Bulb?

UV Bulbs should be replace every 12 -16 months for maximum performance. You can clean your UVC bulb which will add more longevity.

How much do UVC lamps cost to run?

UVC lamps will vary in their running costs. Higher wattage lamps will cost more to run, whilst lower wattage will be cheaper.

I recently wrote a tool which helps you calculate your UVC running costs.

What size UVC do I need?

UVC are rated for LPH (Litres per Hour). If your pond pump outputs at 5,000LPH, then a UVC suitable for for 5000LPH will suffice.

In summary

If you're looking for a lovely clear pond that's not riddled with Algae, then adding a  UVC is definitely the right choice to make.  The main disadvantage is the additional running costs required to keep the UVC on 24/7, but if your fish are much happier then you as a pond owner will be much happier too.

As always, if you have any questions, please be sure to sign up (its free) and leave a comment below.