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Different Approaches to
Building a Veggie Filter |
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Plants and Koi, Can They Live
Happily Together?
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While I am a firm believer
that plants and Koi can live happily ever after in the pond together and
actually benefit each other, I realize that plants in the Koi pond are not for
every one. Everyone wants something different out of the hobby whether it is Koi
pond that contains show quality fish or a water garden that contains both fish
and plants. Many folks enjoy the beauty of the fish and do not want anything to
interfere with that view. I suspect and my email agrees many others consider the
water garden to be an integral part of the over all-landscaping and do not want
or like the sterile look of Koi pond. It is your hobby, do what pleases you and
not what pleases the next person.
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The Advantages |
| Plants readily take up and use two forms of
nitrogen, ammonium (NH4+) and nitrate (NO3_).
In order to understand the nitrogen cycle in our pond it is important to
understand that the conversion of ammonium to nitrite and then to nitrate is
referred to as the nitrification or more simply the nitrogen cycle.
Koi make ammonia and lots of it. Not only does
ammonia come through the digestive tract in the form of urine and feces it also
comes through the gills as the fish breathe. Plants use the ammonia, the first
stage of the nitrogen cycle, to grow. Look at a bag or a bottle of fertilizer
and you will see three numbers on the label. The first number of the equation is
ammonia. Remember we add a high ammonia fertilizer in the spring to make the
grass green up? Ammonia is what makes plants grow and keep their nice green
color. One thing that is really cool about plants is they do not care where the
ammonia comes from. The ammonia that pond plants need to grow can come from
commercially prepared fertilizer or organic fertilizer from fish waste. And as
we all know ammonia is very toxic to fish. One will never see an ammonia reading
in a pond that has plants that are actively growing.
The final stage of the nitrogen cycle is nitrates.
Nitrates form when the biological filter begins to break down the fish wastes.
While nitrates are not harmful in low numbers, after time the nitrates will
build to toxic levels. It is generally recommended that nitrates be kept under
60 PPM. Plants and algae, will use the nitrate. In
the case of high levels of nitrates where there are no plants present, the algae
will form and will cause an algae bloom, the dreaded green water syndrome. There
are only two effective ways to remove the nitrates, water changes and plants.
The second and most common way to remove nitrates is
through water changes. While water changes should be done on a regular basis in
some case it is not practical to do enough changes to keep the nitrates low,
below the 60PPM level. Some of the reasons are: water rationing due to drought,
not having the luxury of well and septic and paying for city water and sewer
usually at a much higher cost than having a well and septic. For some it is a
lack of time because we all seem to lead very busy lives. If water changes can
not be done on a fairly regular basis than plants can be the solution to keeping
nitrates low. Plants can very effectively use/remove nitrates.
Once the water has warmed enough in the spring for
the plants to actively grow, they will begin to use the ammonia and the nitrate
thus eliminating green water or the need for an UV filter. The whole principal
of plants is balance. Each pond is its own ecosystem and one must find the
number of plants to keep everything in balance.
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| The Disadvantages |
| The big argument with plants and Koi is that the Koi
eat/destroy the plants and make a mess in the pond thereby making more work for
the owner. Not all Koi eat or destroy plants and I am not sure why some do and
others don’t. Maybe it is boredom or maybe the fact that Koi are
"eating" machines. There are ways to keep the Koi and plants together
if one is creative. Plant stands either commercially made or homemade can be
utilized to keep the plants up away from the fish.
The biggest argument against plants is that it is
really hard to keep the water clean from the dirt from the plants. Growing the
plants with out dirt can solve this problem. Simply place the plant in a pot and
fill the pot with larger rocks.
Many will argue that plants can harbor parasites and
bacteria that can be harmful to the fish. Rightly so! Treating the plants in a
bath of Potassium Permanganate can solve this problem. Use a hose and wash the
all the dirt off the roots and remove any faded leaves. Then make a solution
using 20 PPM of potassium permanganate in a large container. Place the plants in
the container and add an air stone and let it circulate for a few hours. Now you
have clean plants with no parasites or bacteria with not much effort. I do want
to caution here, do not use formalin to treat the plants or you will have dead
plants because formalin is a herbicide.
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Veggie Filter Design |
| Many of those that do not put plants in their pond
do use veggie filters or sometimes called a bog filter. A veggie filter is part
of the overall pond system but in an area that is not accessible to the fish. It
does not contain any soil. The media for growing the plants can be gravel or
lava rock or a combination of the two. Some will just use larger rocks.
The diagram below shows how we do our veggie
filters. We have used this design for many years with excellent results.
 Just like the water garden, the veggie filter
needs to be thoroughly cleaned at least once a year. Generally this is done in
the fall. This means removing all the plants. At this time you can clean the
plants up, trim them back, divide the plants and then place them back in the
veggie filter or store them for the winter if you live in a cold climate. One
important point is that even if you live in a warmer climate you should still
clean everything out at least once a year. Studying the above design you will
see that it contains a bottom drain for cleaning out the trapped crud. I would
suggest that this drain be opened and cleaned every couple of weeks. But time
and experience will tell you how often you should clean it out in your
circumstances.
(Click to enlarge photo)
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| Calculating the Size of the Veggie filter |
| The first thing you need to know is the volume of
water the pond holds. To calculate the gallons multiply the length times the
width and then multiply that figure by the average depth. This will give you
cubic feet. To convert cubic feet to gallons you would then multiply that number
by 7.48. Some the basic equation is L x W x
D x 7.48 The reason you need to know the gallons is because
the veggie filter has to be sized for the gallons of water in the
pond. A good
rule of thumb is 5 to 15% of the water volume. The higher the fish load the
larger you will need to make the veggie filter to work effectively. And if you
are a real plant enthusiast, you may want to go the 15% just to have a bigger
size that will hold a bigger variety of plants to add to your veggie filter.
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| Sizing the Pump |
The pump size is very important also in your veggie
filter. To figure the pump size you would you need to run the veggie filter,
multiple the total gallons of the pond time 5 to 15% to determine the size pump
you will need. Just to clarify this a little more if your veggie filter is 5% of
your pond volume then multiply the pond volume by 5%. If you are building a
veggie filter that is 15% the size of your total pond volume, then multiple that
by 15%. One other thing to consider is you might want a waterfall that sounds
like a mini Niagara Falls. In this case you would use the larger pump size, 15%
of the total water volume size to give you the noise.
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| Plants to Consider |
| This is really a matter of personal preference of
which plants to use. Some of the plants I have used are Iris, Sweet Flag,
Parrots feather, Bluebells, Umbrella palm, Papyrus, Water Celery both the green
and the variegated, Taro (lots of choices in this family), and Watercress. Water
Hyacinths are a good choice if the veggie filter is in the sun or Water Lettuce
if the area is shaded. I do want to add a word of caution about using either of
these two floating plants. Since the veggie filter is a waterfall it is
important to keep a close eye on these plants. They can dam up and actually
divert the water out of the pond. Here is a fun idea for plants in your veggie filter.
Use edible plants. These choices would be watercress, either green or variegated
celery, water chestnut, sweet flag, flowering rush, and arrowhead. Do an
Internet search for edible pond plants and see what you come up with. When the
plants have excessive leaves I trim them off and feed them to the fish and they
love the treats! My favorite edible plant to grow in a veggie for is a tomato
plant! True hydroponics in the pond. And I feed the fish the leaves and the
fruit that we do not eat. Please be sure to skin the tomatoes and remove the
seeds before feeding them to the fish.
Experiment! Try different plants in your veggie
filter.
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Here is a simple waterfall
barrel with an Umbrella palm. The water falls back into the pond or tank.
In this case the water is falling into a 500-gallon stock tank. But this type of
veggie filter could be sunk into the ground and work as a waterfall in a smaller
pond
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 A larger veggie filter can
be made using a 650-gallon stock tank. This can be a simple as large stock
tub or as simple as a wash tub or anything in between. Size will depend on the
number of gallon in the pond or tank and fish stocking density. The picture
below is a 500-gallon stock tank purchased at a farm store. It flows into a
4,000-gallon tank that is generously stocked with fish. |
At the end of the season the umbrella palms were 6’tall and 5’ across. And the
fish had the benefit of no ammonia or nitrates the entire season.
Water fall filter on a 350 gallon stock tank. This tank also has a bead
filter that filters 1,000 gallons and a home-made box filter that does 100
gallons of filtration 
100-gallon tank has 2 home-made box filters. Each box filter will filter
100 gallons of water each
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