This is an article on How to Build Your Own Koi Pond Filter and the reason I am an authority is because I built my own 6 years ago and it's still going strong!
What exactly is a Koi pond filtration system? What is a fish pond bog?
They are also known as Koi pond bogs. Here is a quick overview of how it works. The bog is normally built at the head of your pond, just behind your waterfall. It is fed from the pond pump which is at the other (far) end of your pond via a 2 to 2 1/2 inch hose. And, once the water has filtered up from the bottom of your bog, through all the lava rock, it will overflow over your waterfalls back into your pond, to be circulated again.
Why not just buy a filter to install since it would be much easier?
Sure, it's easy enough to just go out and buy a fish pond filter that will suit your needs. But, why would you want to when you can build your own Koi Pond Filter? This is a filtration system, that if built correctly will give you years of carefree maintenance.
This article will explain in detail exactly how I built and designed my own Pond Bog and accompanying filter. But, first, let's cover some facts about these filters.
Reasons to build your own Koi pond filter:
If you build it right, this should be last time you should ever need a Koi pond filter. The reason I say this is because once you have built and installed your own pond filter it will immediately start to set up a biological process that will keep your fish healthy and keep your pond water nice and sparkling clean.
Once you build your own pond filter (bog), there is no further need for additional filters. This will save you a lot of money over the lifetime of your pond. You may need to add small pond filters if you decide to add water features. However, these water features use very small and inexpensive filters to keep the water running through them smoothly.
Even though it would be a dirty job to have to clean out the bog in order to get to your filter should your pond develop problems, the chances of this are actually slight to none. As an example, my pond's bog and filter have been in place now, running continuously 24 hours a day - 7 days a week and 365 days a year for over 6 years now, without a problem! And, my pond is about 32 ft by 12 ft by 3 ft. It has approximately 3,000 gallons of water and at one time was home to about 150 Koi. These bog filtration systems work! And, they work beautifully.
The real beauty of the bog filtration system is that the longer it is running, the more a biological balance is built up for the fish in your pond. What is really happening in the bog is that since the water is being filtered through the media, and I use lava rock, it does a very nice job or removing the waste product from the pond itself. The process by which it does this is through nitrification. This means that the nitrifying bacteria (good bacteria) attach themselves to the inside of this bog and on a continual basis, this bacteria eats the excess nutrients such as organic matter and fish waste. This helps create the perfect ecological pond water balance for your fish also.
The typical pond bog, like mine, is constructed at the head of the pond or just behind the waterfalls. The water is pumped from the other end of your pond through a hose and comes out beneath the lava rock that has been placed in your bog. Here it is filtered before once again going over the waterfall back into your pond.
My pond bog filtration system: My bog is approximately 6 foot wide X 4 foot high X 5 foot deep. It is made from cinder blocks or concrete blocks. Although using bricks, stone or any other stable construction medium suited for use underwater is acceptable. After you mortar these blocks together to build your bog, it is necessary to coat the inside and outside of these blocks with a fiberglass mortar and then painted with exterior latex paint. WE DO NOT WANT THIS BOG TO LEAK! After I constructed my bog as above, I lined the inside of it with an EPDM liner that has a life expectancy of around 20 years.
I also let a large portion of this EPDM liner extend from the bog to over the head of the waterfalls. I then placed my large flat stone on top of this liner to give me my waterfalls.
This is how the water is circulated through the bog: A 2 inch hose is run from a pump at the far end of the pond, along the bottom of the pond (out of sight), up to the back and behind the bog. From behind the bog the hose is routed up and over the top and down into the bottom of the bog. It is at this point that the water is filtered. Water from the pump is discharged at the bottom inside of the bog and comes up through approximated 3-4 foot of lava rock. This does a great job of filtration and keeps the pond water clean keeps the fish happy and keeps you happy because your work load and possible filter problems have virtually now been eliminated.
How is the water evenly distributed through the bog's lava rock filtration system? Well, at the end of the hose, there is a pre made piece of equipment installed.
This is simply a length of 2 inch PVC attached to the end of the hose that extends to the bottom of the pond, below the lava rocks.
At the end of this PVC extension is another piece that has already been built before you covered it with lava rock. This piece that is attached to the long straight PVC pipe is connected and glued together to form a U at the end. Now, here is the important part..... You must be sure to cap the ends of the U PVC pipe so that all the water does not just come out in a solid stream. You will now drill as many 1/4 inch holes into the U shaped PVC as you can. It is through these holes that you have just drilled that the water from your pump will squirt out beneath the bed of lava rock.
As you can imagine, water will be forced out under pressure through all the holes in your PVC pipe and filter up through all that lava rock you have laid down on top of it. It is beautifully simple to build and it is one of the best pond filtration bog systems you can have.
The size that you will want to build this PVC piece will be dictated by the bottom width of your bog. Otherwise, if the bottom of your bog is 4 foot then your PVC piece that is shaped like a U at the end should by at least 3 foot across so as to allow as much water to flow through the drilled holes as possible to allow it to filter up through the lava rock.
We are not allowed to submit images with our articles so it is kind of difficult to explain it all and try to get the point across. But, if you want to get a mental image of the shape of the PVC piece, then a close picture of it's shape could be compared to a 2 prong pitchfork. (With the holes drilled in the prongs.)
Of course, you do not have to follow my design exactly either. You can build this piece to suite your own tastes also. For example, you may want perhaps 3 or 4 prongs rather than just 2 and that is fine also. There really is no wrong way to build it as long as the water comes out of the holes and filters up through your lava rock to be filtered, before re-entering the pond via your waterfalls.
