David Larson wrote:

RichToyBox wrote:

David,

As for whether it is best for the water to run upflow or downflow, a well
drained downflow, free to allow air into the media is probably the best and
is known as a trickle tower. If the filter is full and used for plants on
top, then upflow is easier to plumb and maintain a water level. The
bacterial surface area is the same, the difference with trickle tower is the
additional aeration available.

Thanks for the reply! Your idea of the trickle tower makes sense, seeing how this is the method
used in sewage treatment plants.

My next question is this -

Is there is a formula to figure out the cubic feet (or surface area) of filter media one would need?
Let's say the pond will be 3,000 gallons.


OK, I just did a google search on this topic, and I am even more confused now! Some people say the
media surface area should be 5% of pond surface, or 10%, or 1/3 or based on weight of all your koi, or,
or, or ......... YIKES!!!

Isn't there a simple tried and true way to figure this out?

- David