Pond design

Hi Eric
Although not from your part of the world (we are in Surrey) I stumbled across your enormously informative web site and although more appreciative of some aspects there are others that remain a serious doubt to me.

Let me set the scene first. In a previous house some 10 years ago, we built a 10'(l) x 6'(w) x 3'6"(d), pond, the filtration for this was made from 4 rectangualr cold water storage tanks connected together by 2 * 1.5" glued ports, the inlet was a 4" pipe located on an elbow with an extension so that I could draw water from any level in the pond even the surface. Circulation was provided by a Grundfos C/H pump which pushed the water from the outlet of the filters through a UV and back to the pond via a venturi. After some initial problems all the koi seemed to be enjoying their home and we had no losses but did from time to time have some ulcers to deal with. Having said all that the filter system was a chore to maintain with regular syphoning of the filter chambers which entailed removal of the suspended media etc etc - sure you've heard all the sob stories.

Anyway, we have since moved to a new house (the fish were relocated to father in laws Koi pool) and we are now embarking upoin our second koi pond venture. Having read all through the Q&A and various other pages, along with a couple of magazines and other publications, I am still at a loss as to the following and I would be most grateful if you could offer some advice.

The pond we wish to build (gravity fed) and have space for will be @ 12' x 8' x 5' (2-3' in ground, 2-3' above) deep with the bottom sloped slightly to two bottom drains
I have a facility to drain away to sewage waste and intend to valve all filters and the bottom drains so that they can be flushed independently of each other
The area I have earmarked for flitration including pumps, pipework and chambers is some 9' long and could be as much as 6' wide
I also intend to install a skimmer, a waterfall, UV and if funds allow a vertical fluid bed
My questions for you are

1. The surface area of the suggested pond is 96sq feet, most of the preformed fliters such as the Tritech clover leaf designs being 28" diameter only contain 3 chambers giving a total surface area of under 13sq feet (whilst claiming to support a 5000 gallon pond) whereas I need 32 !!!, even some of the inline systems dont give anywhere near 32sq feet - am I working it our wrong, will the fluid bed make this design suitable or should I rethink the size of the pond in the first place ?
2. I intended to fit two c/h circulator pumps from the last chamber - are these man enough for the job as information on gravity external pumps seems scarce and I do like the ease of availibility and replacement (valves allowing) of the c/h pumps, if this is the case should one pump be used for the fluid bed and one for the UV and then both return to the pond just below surface or should I make provision for one or both to feed midwater (assuming back pressure isn't too high either from the pond or the fluid bed)
3. Should I allow for a mid water feed to the filters for during the winter months
4. Should the skimmer be independently pumped and used to feed the waterfall if so I notice u mention using a skimmer for a couple of hours a day, is there any problems in this being an "almost" permanently on feature during daylight hours
5. Can the skimmer feed the fluid bed and then return via the waterfall or should this be avoided as the strainer would have to be so fine that it blocks too quickly
6. Gas heating with an exchanger is not an option I'm afraid, should I see how the temparature fluctuations occur before thinking of an electric heater and if so how can I make sure the provisions are adequate to install at a later date

God - sorry to ramble, every time I think of something it leads to further questions and I DO wish and intend to get this installation as sound as possible with as low a maintenance overhead as can reasonably be expected.

Sorry for the mass of questions but as we are only in the planning stage I want to get these points clear before taking spade to earth. D.M. - Surrey

Hi Darren,

My answer to your questions is as follows:-

1. The figure of 1/3rd the surface area was the generally accepted figure for a pond six feet deep and allowing for the fact that most koi keepers grossly overstock their ponds.
I cannot comment on manufacturers, but quite a few of them are conservative when it come to the size of filter for the size of pond. In many cases the people they cater for have fish other than koi and also have plants in the pond and so do not need such big filters.
There are vortex shaped filters with Japanese matting which do work very well with a smaller size of filter required.
A Fluid bed filter does seem to work well and if added to a filter will certainly allow you to have smaller filters.

2. Central heating circulators are not very popular now and I would not use them as there are many other types of pump on the market. Check out the Koi Carp magazine or Koi Ponds & gardens and make your choice.

3. It is a good idea to have a mid water feed for the winter if the pond is not heated.

4. I feel that the skimmer should have it's own pump and it should be at least 1800 to 2000 gals/hr. There is no reason why the skimmer can't be left on for 24 hours a day and some people do this and run their heaters or other units from them. The reason a couple of hours was mentioned was because some people were worried about the cost of the electricity.

5. At the moment I do not have much experience of fluid bed filters. It would be a good idea to contact the manufacturer of the one you want to use. There are quite a few different types of these filters available.

6. Why is gas heating not an option? I assume you do not have gas.
The electric heaters are much easier to fit so make sure that you have a sufficient length of straight pipe between the pump and the pond so you can fit it. Again it is a good idea to get a catalogue of the heater you may purchase later and check what size it is and make sure you leave sufficient room for it. Eric