Last Pond Q&A of the Year!
Here is today's Pond Q&A, with a question about that dreaded
Hello from Denver,
My neighbor and I have a major string algae problem. We both
have koi and live plants in our pond. The string algae is making
our ponds more of a nuisance than an enjoyment.
Can we use UV equipment in our ponds? We also have a lot of
sludge on the bottom of
our ponds. Please help us.
Carole A. De Herrera
Yes, string algae can definately be a nuisance - and can be tough
to get rid of. First lets look at some of the common causes of
String algae is usually caused by or at least accelerated by
excess nutrients in the pond. The most common cause for this is
over feeding, or inadequate filtration. A little bit of string
algae in a pond is normal, and can be seen growing on the sides
of a well established pond, but when it gets to be over 3/4 of an
inch or so - it can easily get out of hand.
Once it begins growing faster than the ponds natural ecosystem
can break it down, it can quickly take over the pond and become
increasingly difficult to get back under control.
My best recommendation is to first do a thorough pond cleaning
(if possible) and physically remove as much of the string algae
as possible, as well as any decaying organic waste (leaves,
sludge, etc.) from the bottom of the pond, which will also
contribute to the string algae. (See our article on pond
Once you have a clean pond to start fresh, it's much easier to
keep it under control. At this point, I would cut back on your
feeding and start using some of our biological additives like the
Microbe Lift line of products. These will add naturally occuring
beneficial bacteria and microbes into your pond, which will help
keep the excess nutrients under control and help to prevent
string algae from coming back. For more information, I would
also recommend reading our previous article 'String Algae Blues'
on our website here:
As far as the UV - while these are great for clearing green
water, or 'pea soup' algae, they are not effective in controlling
Hope this helps,