"Chip" wrote in message ...
Ques 1: The 1st article says use a mechanical filter before a sand
filter. That is exactly what I am planning. There is a plastic basket
that has fairly small 1/8" slots that all the water from the drains and
skimmer go through before my sand filter. This is easily cleaned.

It's easily cleaned because it's not meant to catch anything small. It's
designed to snag bugs and leaves. A "mechanical filter" is a much more
effective thing. A rule of thumb is that it should filter out anything large
enough to see. Dense plastic mesh, polyfoam sheets, foam pads, enmeshed
brushes, and other materials with very small water passages/openings are
often used for this purpose. Your plastic strainer bucket just isn't enough.


Ques 2: Why not a sand filter w/backwash? BTW, I am converting a swimming
pool into a pond w/ swimming "hole". I would like to use as much of the
current plumbing and filter set-up as possible.

The typical "sand" or "diatomaceous earth" filter will work fine if you want
to take it apart and clean it every day. I'm guessing that you don't. Have a
look at the very good links that Pat sent previously. There are a number of
fairly inexpensive ones available. The difference between a "pool" and a
"pond" is wildlife including bacteria, unseeable algae, fish, and things
that will crawl up your leg. You have to create an ecosystem in the pond to
keep everything alive and healthy. It's more complicated than just not
throwing chlorine into the pool.

In addition, the filter should promote the growth of certain bacteria that
convert nitrogen compounds generated by fish and other plants & animals in
the water to more friendly ones. Shredded plastic, rocks, and other
materials are used to provide a place for these bacteria to live and do
their work. And if you have fish, you need aeration to provide the oxygen
they need.


Ques 3: I read that the veggie filter should be the last thing before
re-entering the pond?

That's correct, although I've seen folks who have a large enough and well
enough constructed veggie filter that they don't even need a mechanical
filter. But the veggie filter ends up being nearly as large as the pond.


Ques 4: These articles don't address what a "settlement tank" is. My
original question.

If you live in the country, you already have one. The septic tank buried in
your yard does the same thing. It is a tank with one or more dividing walls
in it that the water can flow over/under to get from the inlet on one side
to the outlet on the other. Things that are heavy or which floar cannot make
it through and remain in the tank. Occassionally, you have to shut the
system down and clean out the stuff it caught.

Good luck!

Michael
New Orleans, Louisiana USA
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