I also have built an upflow filter out of a 55 gallon drum, and from my
experience the filter you are showing here may be too small (way too small)
for a 3500 gallon pond. Only time will tell, but you may want to be
thinking about larger filters. Neat design, though.

John

"Scott M." wrote in message
...
Hi everyone,

I just discovered this newsgroup tonight and thought I'd share how I built
my own filter and saved a ton of money. My pond is 15 feet by 9 feet and
about 3 1/2 feet deep. I built my own filter as you can see in the
picture.
This filter cost me about $30 Canadian. I went to Walmart and bought the
three drawer unit for $16. I punched a bunch of holes in the bottoms of
the
top two drawers. Basically, the water comes in the top into a black pond
basket full of crushed roch. From there it flows down through to the
second
drawer, which has 4 sheets of white filter material from the pet store
(another $5). From there, it flows through to the bottom drawer, which has
$3 worth of lava rock in it. A pool fitting on the end of the bottom
drawer
allows a hose to be connected to it, providing a gravity fed return to the
pond. I already had the hose and pool fitting and right angle elbow joint
where the water goes into the filter, so I guess you could say the filter
is
worth $50, which is still a lot cheaper than a commercial unit. The
result?
I have crystal clear water. I did add an accellerator to start the algea
growth in the lava rock (my bio filter portion) and Laguna Green Water
Clarifier to the pond and also an aerator to pump fresh oxygen into the
water so I think is is the combination of all of these things that are
giving me a nice clear pond. Anyways, I can give you more details if
anyone
needs them.

Scott
Ottawa, Canada