Question:
Ques 1: The 1st article says use a mechanical filter before a sandfilter. That is exactly what I am planning. There is a plastic basketthat has fairly small 1/8" slots that all the water from the drains andskimmer go through before my sand filter. This is easily cleaned.

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

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

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

Answer: My settling tank is a converted heavy duty rubber cattle trough that pondwater slowly circulates through and then returns to the pond... it's also aplant filter since I have it loaded with pond plants. I flush it out severaltimes over the summer as it has a bottom drain. The muck runs over thelawn - good fertalizer.

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

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

In addition, the filter should promote the growth of certain bacteria thatconvert nitrogen compounds generated by fish and other plants & animals inthe water to more friendly ones. Shredded plastic, rocks, and othermaterials are used to provide a place for these bacteria to live and dotheir work. And if you have fish, you need aeration to provide the oxygenthey need.

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

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

A settlement tank allows the debris time to sink to the bottom. It will doabout 50% of the work.A good one will be circular in shape with a cone shaped bottom with drainfor easy cleaning.The water will revolve in a circle with the clean water leaving at the top.There are other types.