(Click on any picture to see a larger picture.)
I started out ponding in 1994 thinking that I would never need a pump or any filtration. It was during this same time that I did not even know what a Koi was. After a while I realized that a filter would be useful and I found a box filter with a fountain head and tried that. It kept me very busy cleaning it almost on a daily basis to have the fountain working right. Boy, have I come a long way since then. I learned on the Internet about biological filtration and also veggie filtration. Well, I got me some lava rock, pea gravel and pvc pipe and I went to work. Two days later, I could see the bottom of my pond for the first time since I first filled it. I have come a long way since that day too.
Here is what I do now, and the reasons why I do it. I use a liner
but you can use any kind of container. The first thing that you need
to remember is that for a bio/veggie filter to work properly, the surface
area in the filter should be no less than 10% of the surface area of the
pond it is filtering. (EXP. A pond that measures 10' x 12' has
a surface area of 120 sq. ft. A
bio/veggie filter for this pond would need to have no less
than 12 sq. ft. of surface area and if you have a heavy fish load, then you
would need up to 20%.) And it should be 18 to 20 inches deep. I prefer
the liner since it is so versatile in what you can do with it. You
can make the filter above ground using landscape timbers, wall stones or
any other type of material you would like to use.
Or,
you
can put it in the ground as a stream, a pond up stream from your larger pond
or just about anything else you can come up with. It isn't as hard
to conceal the liner bio/veggie filters as it is the container ones.
First, you dig the hole or build the containing walls depending on which
way you want to go with the filter. Then line the area with old carpet
or tons of newspaper for cushioning. Next, lay some pvc pipe across
the bottom of the bio/veggie filter for support of the egg crate. This
pipe should be at least 1.5" in diameter. A vertical pipe will be used
next and it should be a large diameter pipe (I have a pump that fits inside
a 6" pipe so I use 6" pipe). At the bottom of the pipe,
you will need to cut out an arch. Make it so that the top of the arch
is just even with the bottom of the egg crate in the filter. This
will allow you to
access the free space below the egg crate to clean out the gunk. This pipe
needs to be tall enough to to come above the water line of the bio/veggie.
Next, put the egg crate material that is used as a lens in fluorescent
lighting fixtures, all the way across the bottom of the filter area and on
top of the 1.5" pvc pipe. A"T" will cap off this pvc pipe
with a cap in the top to be removed for pumping the water out with a pump
or a Shop Vac and the water line coming from the pump in the pond goes to
the side of the "T".
Now it is time to place the lava rock on top of the egg crate. Be sure and wash the lava rock really well before you place it in the filter. I just open the plastic bag that it comes in and puncture some holes in the bottom of the bags and wash it from the top out in the yard on the grass. It has always been very dusty and you will have a stream of red (or black) water running away from the bags of lava rock. You will need a layer of lava rock 6" to 8" deep.
Next comes the netting. I like using the mosquito netting from a fabric store. You can use any type of netting but the very thin netting should be doubled. By using the netting, you will not have to separate the pea gravel and the lava rock when you have to tear the filter down. Believe me this is not an easy task and the netting really helps. Place the netting so that it completely covers the lava rock. (Lava rock is a great filter media due to its porous structure, which allows good bacteria growth for a biological filter. But over a period of time, bacteria will build up so much that the lava rock will need to be replaced. If this is not done, the whole biological process will go bad and will kill your fish. I recommend replacing the lava rock every two years.)
Now we are ready for the pea gravel but again, you will have to wash it. I bought a pickup load of pea gravel and washed it with the water hose before I started moving it to the filter. Then I continued to wash as I dug into the gravel to try and flush as much of the dust and dirt out of it as possible. Fill the filter to the top with the pea gravel or you can leave from 1" to 3" for just floating plants if you prefer.
The output side of the filter can be made in numerous ways depending on if you have it above ground or in the ground. I use a stream on my Koi pond which allows the water to fall back into the pond and oxygenating it. You can see it in this picture along the top of the picture.
In my smaller
pond, I have the water returning down a wall of the the Windsor Stones in
a waterfall effect. You can see it if you look really close between
the umbrella palm. There is a shoot on either side of the frogs where
the water flows out of the filter and down the Windsor stones.
O.K., it is time to plant some plants in the pea gravel. Use any type of aquatic plant but the ones that have a smaller root system work the best. Water Iris, and Sweetflag are good ones to start with. Some of the other aquatic plants produce roots that are so invasive they will grow all the way down to below the egg crate very quickly. To keep them from doing this, pull them up out of the filter, shake off the pea gravel into the filter and trim the roots back to three or four inches from the plant and then replant them in the filter.
Connect your pipe coming from the pond pump to the side of the "T" in the vertical pipe that was installed earlier. By using a smaller pipe going to a larger pipe, you will be adding oxygen to the water as it falls into the filter. This will aide the beneficial bacteria that require oxygen to live. Also, you will get better flow from you pump, if you use a larger diameter pipe coming from the pump. (Exp.: A pump with a 3/4" diameter output connection will give you more flow rate if you use a pipe with 1, 1.5, or 2".)
You will need to top off your pond when the bio/veggie filter is full. Turn on your pump and be ready with the water hose and the dechlorinater.
To clean the bio/veggie filter which should be done every six to eight weeks, you drop a pump down the large vertical pipe or you can use a Shop Vac hose down the pipe. Use the water coming out of the pump to water your plants in the yard. While you are doing this, you want to take the pump in the pond and hook it up so that you can run the pond water over the top of the pea gravel in the filter. This back washes all the gunk down into the free space below the egg crate without interrupting the biological process. You don't want to use your tap water because it could have chlorine or chloramine in it, which will kill the bacteria that are working for you. When you are finished back washing, top off your pond and be sure and use dechlorinater. Hook your pump back up to the pipe going to the bio/veggie filter and you are in business again.
Consider what
you have just made. You have taken a container, added lava rock and
pea gravel and planted plants bare root into this media. Then you have
given the plants a continuous fertilising with the pond water. Not
only will the plants flourish above the filter but the roots will be flourishing
below the pea gravel. I can not stress enough the need to keep these
plants in check. The way I do this, is to remove the plants early in
the season (around the end of April or the first of May in zone 8). Divide
the plants and then plant them sparsely back in the filter. With the
plants that I have left over, I send out a message to our pond society that
I have free plants and in a day or two, they will all be taken away by other
ponders. By July, I will have more plants to give away. So, when
a ponder stops by to view the pond, I just reach into the filter and pull
them out some plants. They are very appreciative and happy and the
filter doesn't get root bound! If you don't thin the plants out
periodically, your filter will become root bound and it will not function
properly. If left for an extended time in this condition, it could
even damage your pump or cause your pipes to leak or your connections to
come off and drain the
pond.
For pictures and description of how to make a similar filter using a container, go to Skippy's Koi and Pond Page Near the bottom of the page is a link to their biological filter with details and pictures.
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Updated: 10/10/99