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Clearing Up Green Water (Page 2 of 2)

by Elmer Epistola

Posted: September 3, 2004



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The first step in eliminating excess nutrients in the pond is to eliminate all possible external sources of decaying organic matter in the pond.  This includes transferring trees and plants that shed a lot of leaves into the pond, preventing grass and plant trimmings or cuttings from being blown by wind into the pond, and even fencing the pond to prevent small animals from falling into the water.  Fallen leaves and uneaten koi food are the primary offenders under this category, so all leaves and leftover koi food at the pond bottom and water surface must be promptly netted out of the water.



Once the external sources of organic matter have been removed, all that the pond owner has to worry about are the wastes generated within the pond, primarily those excreted by the koi themselves.  As mentioned earlier, the nitrates in the pond are just byproducts of the ammonia produced by the koi, which are first transformed by certain bacteria into nitrites before another set of bacteria transform the nitrites into nitrates.  Fortunately, certain bacteria also consume nitrates from the water.


The key to removing all these harmful compounds from the pond water is proper water filtration.  Filtration accomplishes two major things:  1) it physically removes most of the decaying organic matter in the pond and 2) it triggers the ammonia-to-nitrite-to-nitrate cycle by providing home to the bacteria that perform the various tricks behind it. 


Your filter must have a water capacity of no less than 10% of your pond volume and your filter pump must be capable of turning over the entire volume of your pond in one hour.  Aside from this, the filter media must be properly chosen to accomplish the mechanical and biological filtration effectively.  For more information about proper filtration, please see the article, "The Basics of Koi Pond Filtration."


Another way to limit algae's access to nutrients, although it should only be considered as a complement and not as an alternative to filtration,  is to put other plants in the pond.  Many plants have voracious appetites for pond water nutrients, so having them in the pond will deprive the algae of nutrients.  One problem with this is that plants don't thrive too well in ponds with koi, since the latter loves chewing on them.  There are ways, nonetheless, to enjoy both of them in the same pond.  See the article 'Protecting Plants from Koi.'


Partial shading, good water filtration, and complementary plants in the pond should be enough to give you crystal-clear water.  If not, then you may need the help of ultraviolet lamp systems designed to kill algae and make them clump together.  You can put the uv lamp assembly before your main filter, so that the dead algae will not be returned to the pond.  Many koi enthusiasts consider the uv lamp system as a 'must-have' in order to get crystal-clear water, but I am not one of them.  I think that a properly-sized and well-designed pond filtration system should be enough.  Lastly, it would be worthwhile to shell out a few more bucks to get a surface skimmer for removing dissolved wastes from the water, especially if you live in a country with a hot climate. 


If you are one of the many koi hobbyists who are still struggling to get rid of algae in their ponds, don't lose hope.  Unlike turning water into wine, turning green water into a crystal-clear one needs no miracle.



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