How To Clear Algae From A Fish Pond | The Problem With Using Pond Algaecide

Pond Algae Newsletter From James Lord

The scourge of many pond keepers is the all too common green or brown cloudy water caused by suspended floating fish pond algae. Often referred to as "Green Water" this is a common nuisance for the majority of pond keepers, particularly during the sunny summer months.

Many pond keepers use pond algaecides as the preferred way of controlling fish pond algae. The fish pond algaecide business is an extremely large and lucrative business surrounded by myth. As to whether these chemicals benefit the pond and are as successful a way to clear algae from a fish pond as they are supposed to is a matter of opinion.

My opinion for what it is worth is that pond algaecide chemicals also known as algae killers do more harm than good and work very ineffectively... That is just my opinion by the way.

One thing I do know however is that your pond will need treating frequently and the costs soon build up. There is also the hassle of measuring and treating at the correct dose so as to not poison fish or destroy beneficial nitrifying bacteria that live on the pond filter media.

I was prompted to write about how to clear algae from a fish pond after receiving this question from James who is a subscriber to my free weekly newsletter articles ...

James initial email...

"Many thanks for your quick reply relating to my sludge problem.

I installed a biological filter and a separate UV clarifier into my pond to purify the water of ammonia and nitrite and to also kill the green water (suspended algae).

I also decided to use a a product called POND MAGICIAN and the instructions say that UV light will kill off the living beneficial micro-organisms that are in the product and that multiply in the pond.

I therefore decided to stop using the UV clarifier. To my surprise the amount of green fish pond algae has increased and my pond is starting to look quite murky.

Have you got any advice that may help me to clear fish pond algae?

Thanks

James"

My initial reply...

"Hi James

The green algae in fish pond scenario is all too common for many pond keepers and many pond algaecide manufacturers will claim that UV light will destroy the natural beneficial micro organisms contained within their product.

There isn't a UV Clarifier sometimes known as a UV sterilizer (although technically they are different) in existence, specifically designed for pond use that will destroy bacteria to any great extent.

The bacteria are also not floating around the pond but are fixed in place to all pond and filter surfaces. Remember that pond water containing algae is pumped through the UV clarifier in order that algae is exposed to the UV.

UV light is used to a large extent in the food and pharmaceutical industries as a means to sterilize and disinfect. These units however are specifically engineered for this purpose, are far more powerful and and require much slower flow rates than any UV Clarifier designed for use in a garden fish pond.

The reason for fish pond algae bloom (murky water) is due to 3 possibilities

  • The UV wattage is not powerful enough for the size of your pond
  • The UV lamp needs to be replaced.
  • The quartz tube inside the UV Clarifier needs a routine clean.

A UV will not kill any type of algae that does NOT flow through the UV i.e. blanket weed algae also known as blanket algae, hair algae, string algae and blanket weed.

The differences between a UV Clarifier and a UV Sterilizer...

Although many people myself included use the terms UV Clarifier and UV sterilizer to mean one and the same thing there is technically a difference.

UV in industrial food applications is used to destroy pathogenic bacteria that might be present as well as water borne viruses.

The product is known as a UV Sterilizer. These Sterilizers are not used in ponds. In a pond you would use a UV Clarifier that clarifies or cleans the pond water.

A UV Clarifier is much less powerful than a UV Sterilizer and a UV CLARIFIER will not kill MICROBES.

how to clear algae from a fish pond

The best solution to keep floating algae at bay in a garden pond is to install a correctly specified (sized) UV light. This system works all the time every time so long as it is sized correctly and so long as the maintenance required is carried out.

what is the difference between algae and blanket weed?

Filamentous string algae also known as blanket algae, hair algae, string algae and blanket weed can be seen attached to any available pond surface or floating on the pond surface itself. This algae unlike suspended algae is much larger and can not be destroyed using a UV Clarifier.

To control blanket weed algae use Viresco Blanketweed Solution which is long lasting and is proven to work... many tests by independent experts have proven the efficacy of Viresco.

Regards