For the filter system as a
whole we take the actual volume of your pond and then
add to this volume various "conditioning factors" to
take into account your particular circumstances.
We add 25% if your pond is in
full sunshine - because if it is, the water will warm
up quicker, and algae will grow faster.
We add 25% if your pond is less than
2' 6" deep (75cm) - because a high percentage of the
water in the pond is exposed to the full power of the
sun and algae will grow faster.
We add between 15-35% to your pond
depending on where you live, if the pond is in Manchester
in the UK, its going to be cooler and less sunny than
if the pond is in Florida USA. If it is hotter and sunnier
then algae and fish will grow faster.
This then gives us an effective pond
volume, which is the amount of water we need to filter.
For a filter to work though, the entire effective volume
of the pond has to pass through it approximately once
every two hours.
A pond 0.9m x 0.9m x 0.9m (3'
x 3' x 3') in full sun in Cape Town (South Africa) would
have an actual pond volume of approx. 730 litres (160
In this example we would add 25%
for the pond being in full sunshine and 35% for the
lovely Cape Town climate giving a total addition of
60%. Therefore, we must filter the ponds effective volume
of 1170 litres (275 gallons), and any pump used should
have a flow rate of at least 585 litres per hour (130
gallons per hour).
So we would filter the pond as though
it had 261 gallons of water in it, and any pump we use
should have a flow rate of 130 gallons per hour.
If you would like us to recommend
a guaranteed filter system please visit our interactive
Pond Selector pages.