Water Gardens Gazette number 302

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2. Why you need to know the volume of your pond ........

A. In a lake or natural pond you will find relatively few fish.
A natural water system can only cope with a certain fish density
in view of limited food sources and biological capacity.
Many lakes have lots of small fish which are stunted. The capacity
is based upon total weight essentially - so you can have many
small fish competing for scarce food or less large fish.
Where you find large fish they eat the small fish in egg or
fingerling stages.
In a pond there are almost always too many fish and that is
why a biofilter is absolutely essential. To be able to build
or buy the right pond filter you must know the pond volume.
The volume of water together with the stocking density determine
the physical size and more importantly the amount of biomedia
required to create a good biofiltration system.
Take the following information as a rough guide (you can always
add more but not less biomedia) for how much biomedia you need
to treat a pond volume of 250 gallons or 1,000 litres

Plastic tubes 1 inch diameter and 1 inch high (hollow): 8-10 gallons
Plastic balls 1 inch diameter: 12-15 gallons
Lava rock: 2 gallons
Open cell foam: 5 gallons
Alfagrog sintered ceramic: 1/2 gallon

Multiply the above by 4.5 to convert to litres

Biomedia is of course the surface upon which the bacteria
responsible for keeping the pond water pure reside. Obviously
the greater the surface area then the more bacteria you can have
and the better your biofilter will perform.


B. Pond volume is also required to specify the size of the Ultra
violet light you need to prevent algae making your pond go green
For a pond of around 250 gallons in full sun and highly stocked
a 4 watt UV will do the job. This will also be big enough for a
pond with very few fish and situated in the shade of 700 gallons.
This assumes the UV comes equipped with a quartz tube to ensure
the UV runs at peak efficiency.
FOr a pond with average stocking an 8 watts UV will handle
pond volumes up to around 1200 gallons depending upon sun/shade
situation.
The rule is as follows:
Lots of sun, lots of fish, high water temperature then more UV
power will be required. If you find you have specified an UV
that is too small it is possible to add an extra one of the same size.
For example 2 by 4 watts units is the same as an 8 watts unit.

c. If you ever need to add chemicals to your pond then knowing the pond
volume is critical. The reason is because all treatments work on the
principle of so many ozs per 100 gallons, gms per litre and so on.
Taking a chance or guessing the volume may kill your fish.

d. A fourth reason you might need to know the pond volume is to be
able to specify your pond pump. However this was covered in detail
by the calculator offered in the previous edition. Remember you can
still get the calculator here:

Free pond calculator go to this page to download the pond calculator
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QUICK TIPS QUICK TIPS QUICK TIPS QUICK TIPS
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Today's quick tips ..........

1. If you have a pond and the depth is not constant take a stick
and mark it in intervals of say 3 inches with an indelible ink pen.
At 10 different places in the pond insert the stick and record the depths (10 numbers).
Add the numbers together and divide by 10.
Use this answer as the average depth of the pond.

2. If your pond is of equal depth and the same cross section
then you can accurately measure the pond volume as follows.

Measure the depth using a tape or stick.

Using the pond pump measure how long it takes to fill say a 5
gallons container.

Now pump water out of the pond for say 5 minutes

Record the depth after pumping out water

The pond's volume is then calculated as follows:

S = depth of pond in inches or any unit before pumping starts
D = inches or any unit of water pumped out of pond when pumping stops
T1 = time to fill the container
T2 = time pump was run to pump out water
V = volume of container

Volume of pond = (S x V x T2) DIVIDED BY (D x T1)

Example:
S = 30 inches
D = 3 inches
T1 = 1 minute
T2 = 10 minutes
V = 3 gallons

Pond volume = (30 x 3 x 10) divided by (3 x 1)

= (900) divided by (3)

= 300 gallons

If container was in gallons then final pond volume is in gallons
If container was in litres then final pond volume is in litres

It does not matter whether you measure depth in inches or any other units.

Use the pump to pump out water in the same position used to fill the
container.

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New articles published on our web site ...............

In case you are not aware of the articles we publish by leading
experts in the water gardening field take a look at one of our main sites which
covers all kinds of topics related to water gardening where you will see the list.

Peter May, one of the leading UK contributors, is just starting his
own website and maybe you would like to see what he has to say
there. This is his web address where you will find the details:
of the Perfect Pond Detective He would appreciate your
visit.

Peter is a real expert in the practice of water gardening. He
even dug all his own holes for many years. He offers consulting
services and does talks at very modest rates throughout the UK.
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Web address where all editions can be found and where you
can ask questions we will try to answer ..............

Our water gardens gazette index page is here

We will try to answer personally but if this proves to be not
possible because of large volumes of e mail we receive we will
certainly answer in future Gazettes.

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