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I’m tired of fighting algae. Will a UV take care of all the algae growth? | Decorative Ponds & Water Gardens Q & A


Q: I’m tired of fighting algae. Will a UV take care of all the algae growth?

Q: I’m tired of fighting algae. Will a UV take care of all the algae growth?

Cherice – Everett, GA

A: Who isn’t tired of battling algae!

Caused by excess fish waste and dead organics from leaves or previous algae blooms combined with excessive spring- and summertime sunlight, all that garish green growth looks horrible, ruins your water quality, and creates a headache for you and your fish.

Is an ultraviolet clarifier, like The Pond Guy® PowerUV™ Clarifiers or the AllClear™ PLUS Pressurized Filter the answer? It depends on the type of algae you’re trying to destroy.

Know Your Algae

The algae that forms in your pond comes in two basic flavors: planktonic and filamentous.

  • Planktonic algae, the source of pea soup algae blooms, are floating, microscopic plants that color pond water shades of green, blue-green, brown or variations in between. In controlled amounts, this type of algae can actually be beneficial. It’s considered the start of the pond food chain as the tiny plants feed fish inhabitants, and it can also shade the pond’s bottom, preventing subsurface nuisance plants from growing. In uncontrolled amounts, however, planktonic algae can cause oxygen depletions and fish kill.
  • Filamentous (string) algae are single-celled plants that form long, visible chain, threads or filaments. These threads, which start growing along the bottom of the pond in shallow water or on rocks or other aquatic plants, intertwine and form mats that resemble wet wool. When these mats rise to the surface, they’re commonly referred to as pond scum. These mats make great homes for micro- and macro-invertebrates, like bugs and worms, but they’re also unsightly.

UV clarifiers work by destroying the ultrafine planktonic algae – but, unfortunately, they do nothing to combat the filamentous algae. You’ll need a different strategy for the stringy stuff.

Battling Planktonic Algae

So how does ultraviolet light fight planktonic algae? When the algae cells are exposed to the bulb’s ultraviolet rays, radiation destroys the plants’ cellular walls. As a result, the tiny particles of dead algae clump together, and those clumps are then removed by your mechanical filtration system.

For the UV clarifier to work properly, however, follow these guidelines:

  • Replace bulbs yearly. Worn-out bulbs – even if they still light up – may not be as effective at controlling green water.
  • Watch your flow rate. Pushing water past the UV too fast can damage the unit and not allow enough contact time with the UV bulb for it to be effective.
  • Don’t flow too slow. Running a UV at too slow of a flow will act as a sterilizer and may also have a negative affect on natural bacteria meant to help decompose dead organics and fish waste.

Finding Balance

If you have an algae problem, be it planktonic or filamentous, it indicates your pond is out of balance. An ultraviolet clarifier should actually be one of your last tactics! Add some beneficial bacteria from the Pond Logic® DefensePAC® Pond Care Package to help reduce the amount of organics in your pond. Start aerating the water. Consider using pond dye. If you have a thriving fish population, think about finding a new home for them (but don’t release them into the wild!). Manage the nutrients, sunlight and oxygen levels, and your algae proliferation should naturally level out on its own.

Pond Talk: How dependent are you on your ultraviolet clarifier?

Eliminate Green Water - The Pond Guy® PowerUV™

8 Responses

  1. string algae I usually take a brand new bought toilet cleaning brush and went around my pond and wound the string algae. Not a permanent fix but a quick fix 🙂

  2. What is the flow rate for needed for a 13W UV…..???
    JROTH

    • The flow rate may be slightly different depending on the design of the UV you are using. For The Pond Guy® PowerUV™ a 13W unit can be used for ponds up to 2,200 gallons and allow for a maximum flow of 1,200 gph.

  3. Kudos for your advice! UV should be your last choice. Barley products will also help.

  4. After installing a new All-clear biofilter and 2100gph pump and treating the 4000 gal pond with the recommended Pond logic defense, and running an aerator, this pond has only some goldfish and still the water remains very turbid two weeks later.

    • Hi Alan, Keep up on the routine maintenance and results will follow. Are you still fighting green water or is the pond now just cloudy?

  5. I had the same problem, but it was string algae on my Waterfalls. My water was always clear because I had a UV. The algae would build on the waterfall rocks as soon as it hit 70 degrees. This was a problem for me for 13 years. On 15 March 2015 I bought an IonizerGEN2 and installed it. The waterfalls are completely clean and I can really enjoy the pond without the added maintenance. The Ionizer is a bit pricey, but certainly worth the money.
    So I recommend the UV and the Ionizer.
    Problem solved.

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