Hi,
First of all click on my link below to have a look at my pond, koi and filter which will give you some idea of what is involved in koi keeping which I have been involved in now for over 30 years, having koi living that long in the environment I have made for them,BUT according to some koi keepers I am living in the stone age because I WILL NOT go for all the new gadgets that keep being invented for better koi keeping (better than 30 years I don't think so) you just have to visit a koi forum to see what the topics are from UV filters to trickle towers you name it.
My pond is concrete and is done in two halves the first pond was not large enough so I built another one along side it and then joined them together the first one was a liner and after twenty years it started to leak so I concreted that as well.
I wouldn't recommend putting large rocks on a liner no matter what you put under the liner to support them because eventually it is going to pierce the liner,
George.

Here is a link that might be useful: George's Japanese Garden

"koi people" would cover a wide range of opinions - see the pond forum for a lively discussion. My experience in New England leads to the following advice:

- The size of the pond does matter. Small ponds are susceptible to rapid changes in temp, pH, water quality, etc. 9000 gal is fairly stable, but still needs frequent monitoring during the warm months.
- EPDM liner ponds have limits on design that you will have to accept if you want to use your liner. The comments above are mostly consistent with my experience. Hide the liner for looks and lifetime, accept the maintenance issues.
- INSTALL A BOTTOM DRAIN. Also a gravity feed to the first filter. Few things will make life easier when maintaining your koi pond.
- reconsider the size of the rocks you plan to use. I love big stones, but you cannot safely handle 3000 lb stones on a slope with a couple of strong guys. Consider hiring a tracked excavator for a day. Minimal ground damage, and you can place a lot of rocks if you have the straps, some rock moving bars and some help for the operator.
- placing big rocks on liner is creating a future problem. Sorry, but all the good advice is only minimizing a future weak spot. Just holding the liner down in one area means it will be stressed. The small smooth rocks are the best approach, built up carefully.
- ignore the advice from "koi people" about rocks in the pond. I have a natural rock walled pond with hard granite walls and many exposed stone edges and never saw a koi injured. Some people like a very sterile environment with no natural surfaces to maximize the number of fish in a gallon of pond. I call that an aquarium.
- Steep sides are a good deterrent to raccoons and herons, although they don't matter much to osprey, cormorants, and kingfishers. You have to figure out how much wildlife you will deal with. I now have moose in the woods behind my pond and am hoping they don't come over for a swim.
- Koi will eat some plants and root around in most dirt or mud areas, and if you have prized plant specimens you might want the separate area. Having some hiding areas does provide cover for small fry until they are big enough to swim with the big guys. Good Luck.

I'm glad to see these comments before building the pond (although dismayed to become confused again after lots & lots of research & even a paid consultant). Nice garden, George! I guess I need to be more careful generalizing about 'koi folks' and 'water-garden folks'...more accurately maybe is that I've seen lots of 'koi and water-gardents are incompatible' type of comparisons.

Here are some websites which exemplify and display the reasoning for some of these ideas:

some of the many recommendations for using straight sides to keep out predators:

http://www.ponddoc.com/WhatsUpDoc/Design/PondPlan.html (see 'Avoid Plant Shelves')
http://www.arborman.com/koibeg.htm#2.%20%20How%20Deep%20and%20How%20Big
http://www.koivet.com/html/coolstuff/letters_details.php?letter_id=7
http://www.bestwayimportedkoi.com/pondtips.html (see #5)
http://www.urbanfarmerstore.com/ponds/pondintro.html (under 'raccoons')
http://www.mnwgs.org/articles/Aqtwlife.htm

No rocks:
http://www.ponddoc.com/WhatsUpDoc/WaterQuality/CessPool.html (read this one!)
http://www.aquaart.com/Cuny2.html
http://members.core.com/~klee365/diff.html (and straight sides)
(the pond forum has had a lot of pro- and anti-rock discussions)

Many have written that it is difficult to keep koi and plants in the same pond:
http://www.tomskoi.com/watergardens.htm
http://www.sacramentokoi.com/ponddesign.htm#5)%20How%20important%20is%20the%20shape%20and%20bottom%20contour%20of%20the%20pond
http://home.netcom.com/~larry_l/intro_to_koi.htm (under 'Plants in the pond')

Another thing I've been told is to not use sand under the liner, as it can shift over time:

http://www.ponddoc.com/WhatsUpDoc/Design/PondPlan.html ('Don't Line the Bottom with Sand')

chuckling,...
Mark.. I do not think it is a case of this practise is good or this one bad, moreso, it is an entire package...
ie: sand shifting.. sure if the sand was not tamped wet, the person did not install stone and if the excavation was not done correctly in the first place.

If there is time, I'll go through some of the sites, considering that they get my nose all in atwist... in the end result, we're the people that get called to fix the d--n things when the builder can't be found again. As a sidebar, I'm always learning new tricks and methods, perhaps I'll learn a thing or two. Though, on the pond subject, for once,.. not likely..... I've made too many, far far too many mistakes and learned from them all,....
ie: system, because of the EPDM material, the bottom drain will need to be a self priming hose with screens. Perforating the lowest corner would be too risky for longterm use. The less moving parts the safer it will be.
Develop your own solution, and keep asking for specific solutions to specific problems. ie: how to put in a bottom drain in an EPDM liner, that will never leak.
edzard

Mark -

You will never find a single design that all the "experts" agree on, but if you consider the advice as single perspectives about the tradeoffs among various choices, it will start to make sense. Since this is a Japanese Gardening forum, I assume you don't want the sterile look of a smooth sided, totally clear water aquarium. When I can see my koi at the bottom of a 6' deep pond, I think the water is too clear. Many people would disagree. I have about one fourth of the "possible" koi density, a choice based on my view of koi as a beautiful part of the garden, not the main attraction. That makes many design options available that would not be there if I wanted to maximize the pounds of fish per hundred gallons.

I read the links you posted and think there is some consistency:

Steep sides - they definitely inhibit racoons and herons, and those are the most common predators. They are easiest to achieve with concrete or fiberglass ponds however.

Rocks - two issues here; the "koi damage from sharp rocks" and the "rocks trap debris on the bottom" issues. The first is a bigger issue if you have big, valuable koi. Mine, including some up to 24", don't have a problem with self inflicted wounds. The debris trap in rock crevices problem is a huge debate, but it can only be understood by including the filtration, fish loading, feeding, climate, and maintenance issues. No simple answer, just a balance of investment, effort, and results.

Plants and Koi - No serious koi breeder wants plants and no serious water lily grower wants koi. Many people have both and accept the consequences.

Sand under liner - What else do you use? Carpet over gravel? The only thing I might consider over compacted sand is the portland cement and vermiculite mixture that many vinyl swimming pool installers use under the liner. It takes skill to mix, place, and smooth, but it sets up nice and stiff, although it doesn't have any tensile strength.

In short, don't obsess over a perfect set of design guidelines. An experienced installer who maintains his/her work is the best help.

good points LW,..
in the previous post it was specified that rounded stone be used and that sand again fills in the gaps, into which it is set. This makes for a very smooth bottom that gently undulates. In cleaning such ponds, we go in barefoot... obviously there are no sharp stones.

I have to wonder with the steep sides what the loss is to predators or to jumping fish. Considering they do appreciate warm water from time to time, a central swale is often built acting as a sandbar, which is far enough away from the 4 footed predators yet unfortunately wide open for 2 legged avian predators. 'suppose it depends on what risks one is willing to take.

edzard

Good analysis, Louis...I'd also like the fish to be part of a beautiful garden, not the main focus.
I have two other factors to consider for rocks in the pond that I hadn't thought of before. The pond is located next to a flood zone where the water table could conceivably rise up, beneath tall yellow poplars--80 foot trees that drop huge limbs from time to time (up to 15 feet long, perhaps 100 lbs). The rocks could a) provide weight to counterbalance a rising water table and b) protect the liner from falling limbs (thanks to Edzard for asking how I would protect the liner). I've got a few more specific questions:

x) When using a bottom drain, you can't use sand in the pond, can you? I would think that sand would get swept down into the bottom drain.
x) Are river rounds good rocks to build up the sides? The rounded edges lessen the chance of liner punctures and fish injuries, but might not interlock as well as more-angular edges when building rocks up the side.
x) What would the maximum stable slope for river rounds (or other rocks) be? 60%, as Edzard mentioned? Should I choose more angular (yet not sharp) rocks for a steeper angle?
x) Would this maximum slope be steep enough to discourage racoons and herons? Would it be good to put overhanging rocks above the rock slope to discourage them?
x) Beneath the liner, is a particular grade of sand needed, or is inexpensive all-purpose/playground sand fine?
x) Should a wood deck next to or overhanging the pond be avoided, since wood decks need periodic water-proofing and the water-proofing material could get into the pond?

Thanks!

Hi Mark,
If you intend putting a bottom drain in it is usually to take the bottom water to a filter and if you are going to filter your water you will not want any thing small like sand or gravel in the pond. If the water goes part way up the rocks at the side of the pond and some rocks overhang the water that will give the pond a more natural appearance, and what ever stones or rocks you decide to put in your pond the smoother the better as something sharp will eventually pierce the liner ,whether its now or in the future,its not worth it.
George.

Here is a link that might be useful: George's Japanese Garden

Glad I can help, but I don't want to overstep my experience, so I will answer the questions where I have some hands on knowledge.

Bottom drains - they will sweep any sand in the immediate vicinity, but have no effect on things a foot or two away as the velocity is negligible. The idea is to get solids to fall to the lowest point and get swept away. If the solids sit in rock crevices two feet away, they stay there. This is the source of the "rock bottm vs smooth bottom" discussion.

River rounds - if you have them available, great. If you have to buy them by the bag, you are going to spend a lot to cover a 9000 gal pond. You understand the tradeoffs here- smooth doesn't stack well, but othewise is great.
I doubt you can get anything over 30% with rounded stones. There are actually engineering formulae for determining the max stack angle for differnt shapes and density of material, but I don't think pond builders worry about them.

Any slope that goes to the edge can be used by raccoons and herons. I find that having a deep pond where the fish can get away from predators helps a lot.

I haven't used overhanging rocks.

Sand is graded by size, source, and shape. You want a "sharp" builders sand for it's ability to pack. Playbox sand is usually too fine and rounded. Not the most critical issue however.

Overhanging deck - a great Japanese design style that works the wonderful contrasts between man made/natural; linear/irregular; water/land; static/changing and many others. See my posts for one example. I use Ipe because it weathers to a beautiful grey, doesn't need any maintenance or finish, and doesn't contain any toxic metals to drip into the water. It has natural toxins of course which make it durable, but I don't let too much in the water. I have dropped a few pieces in by accident (it sinks like a stone) and haven't noticed any effect.

I hope the rising water table and tree limbs don't damage the liner. Swimming pool installers (gunite and liner) often use a reverse drain valve meant to allow water in if the pressure is higher than the pool. The big tree limbs probably won't penetrate a rock lined pool but what about the roots? could be an issue digging and in the future. Good luck.