Your filter system design, sounds like the one BV put in. It is a very good
design. Do a Google for BV pond design. The use of a bottom drain should
be for continuous operation, cleaning the bottom of the debris as it
accumulates. The koi move stuff on the bottom, and the current to the
bottom drain, keeps the stuff moving in that direction. Having it used only
intermittently to send stuff to waste will not do as much to keep the bottom
clean. A skimmer is highly beneficial in catching leaves and other debris
and removing it from the pond before it has a chance to settle. I think a
skimmer is more important than the bottom drain, but I think you should have
both. The added tanks will not only increase the water volume, but if they
were filled with some filter materials like SpringFlo would be very good
improvements in the total filtration. If the tops were left off, then they
could be planted with floating plants, like lettuce or hyacinths that would
help to reduce the nitrates in the system.

A general rule around here says that for the first koi, you need 1000
gallons of water and 100 gallons for each additional koi. They grow to be
rather large. If you can, make the pond deeper. Deeper takes little more
liner, gives large increases in volume, allows the koi to exercise in the
vertical mode which is beneficial in their growth.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Iain Miller" wrote in message
...
Planning my first pond & got to the point of working out how to hook up
the
filters etc......

I was planning on having an external filter at the same level as the pond
so
that water will flow into it & then putting some kind of pump on the clean
side - the logic being that it would be better to just suck the rubbish
out
of the pond into the filter (possibly into some kind of catchment chamber
first) rather than "liquidizing" it through a pump before it gets to the
filter.

Assuming I do this then I need to get water out of the pond - a bottom
drain
looks like a good idea but cutting the liner down there looks like an
"interesting" thing to attempt & also presumeably I'd have to dig a trench
of some sort under the line to accomodate the pipework....

Another solution I was advised to look at was to have a bottom drain that
just went to a waste pipe so that periodically I could just open it & suck
the rubbish from the bottom of the pond straight to waste. Then to mount
the
outlet for the filter about halfway up the side of the pond. The other
question related to this is as to whether its worth putting in a surface
skimmer or not.

The area my pond will go in naturally restricts the size it can be (we are
only talking about 1000 gallons or so). However, there is a redundant (and
non visible) area close by where I was considering placing some larg-ish
water tanks (with lids on) - the idea being to pump water out from the
filter upto these which would then overflow back to the pond. The idea of
is
to increase the overall water volume of the system.

Has anybody tried to do something similar & what's the general view as to
how succesful/beneficial this might be? I could potentially increase the
water volume by between 25 & 50% by doing this (at a rough estimate).

I've kept aquariums for a number of years so I know a fair bit about water
chemistry & management, filters, bio cycles etc but this will be my first
pond. I grew up with ponds in the garden but these were always completely
unfiltered & seemed to do OK (depending on the weather and the frequency
with which the Herons visited!). I would like to try & build something
that
needs relatively little maintenance & although I might put a few Koi in it
I
do want to have some plants etc to make it fairly natural looking.

All ideas gratefully received.

I.