Not to hijack the other thread, here is our pond set-up and
maintenance. It's a total inexpensive DIY system. Nothing is
fancy ...it's Rubbermaid type filter tubs, regular PVC tubing, toilet
flanges, etc...purchased at Home Depot. It would make a snobby
koi keeper laugh out loud. But, hey it works, and does the job.
We have 17 large koi that love their habitat.

The mechanical filters consist of three 35 to 45 gallon rubber maid type tubs, daisy chained together.
The first tub: In the first tub is standard filter material to catch the heavy stuff. This filter material is several individual pieces of filter material rolled up and packed in between dividers (At one time we used to use Dacron batting, but found it difficult to clean.) The clarity of our water determines the frequency of cleaning the filter material in this first tub. The cleaning ranges from two tines a week in early spring (due to the tannins from the large oak trees we have) to once a week, later in the season. The clarity of our water governs this task. Most of the fish waste gets caught in the first tub.

The second tub: The second tub is again divided into three seperate compartments. We cut the sides off of plastic crates and made three plastic sleeve. Each sleeve is wrapped one time with standard type filter material that we purchased at the pond store. This filter material is specifically for mechenical filteration and every pond supply store has it. This standard filter material is much easier to clean than the Dacron batting. These wrapped sleeves are standing upright in the tubs and are cleaned usually one to two times per week, again depending on the clarity of our water.

The third tub: The third tub houses the five pumps and behind the pumps is a fine mesh pad that we purchased in an equiptment rental store for 10.00 dollars. (It is the pad that is placed lastly on a floor sander to finish the job. ) This pad is usually cleaned once a week. Whatever makes it through the first two tubs gets finally caught in this last pad. We call the last tub "the polishing tub' as it gives the water it's final 'polishing' before exiting and making the journey to the biological pond, which does the final scrubbing of the water before reentering the main pond again...Again the clarity of the water as well as the water flow in the last tub governs the frequency of cleaning. As soon as we see the water flow slow up in this last tub, we know the filter materials are getting clogged and need to be cleaned.

The beauty of this system is... as your pond and fish grow--so can your mechenical filteration system--just daisy chain another tub on. We started out with two tubs and as our pond grew and our Koi grew we added one more.
We have a lot of large koi and as you know Koi make a lot of waste. The maintenance routine I have described is our usual routine. Our pond is always clear, the clarity of our water always ranges from clear to cystal clear to gin clear.

We attribute the health and clarity of our pond to two things, Firstly--The frequent water changes that are done each week by adding fresh water each day for ten to fifteen minutes, thus resulting in a 35 to 49% water change over a one week period. We never partially empty our pond and do a large water change at one time.

Secondly--The frequency in which are filters are cleaned. If you want to maintain a clean and healthy pond with cystal clear water, you have to keep on top of cleaning the filter pads.

Biological Pond review...
The biological pond is located 18 feet from the main pond it is a 200 gallon
pond filled with plants and zeolite rocks. The water leaves the last filter box and travels underground to the bio pond, travels through the bio pond getting scrubbed by all the vegetation, then exits the bio pond and travel back underground and re-enters the pond from under a small wood dock
in back of the main pond. We added the biological pond in 1998.

The shimmer only used in early spring and fall and is located under the
small wood deck.

Note, We never vacuum our pond or had to vacuum our pond. Our pond is bare bottom with the exception of our pebbled beach. During our daily water additions, we sometimes lay the water hose on the bottom of the pond to sweep all the mulm toward and into the bottom drain. We clean our beaches and shelves the same way, by using the hose to release the muck and mulm that gathers around and between the rocks. In the beaches we swish the rocks around and turn them over to release any waste or fish food that gathers in between and under the rocks.
No UV Light and No Chemicals...We also do not use any chemicals or use a uv light. There is no need for it, as our pond is always clear, we maintain clear healthy water with frequent water changes and keeping the filters clean. We believe the uv light also kills the good bacteria.