Today's successful water garden usually is designed as an ecosystem that uses a balance between fish, plants and bacteria keeping the water clear. The type of pond I'm talking about is self-contained (not fed by a spring or stream) and between 100-900 sq ft; a backyard water garden that is easy to maintain and adds value to your lifestyle and property. 20 years ago the typical do-it-yourself water garden was a muck-filled cesspool waiting to happen, while the successful koi pond required deep water and unattractive out of the pond filtering equipment. Thanks to a better understanding of the pond ecosystem and some equipment ideas borrowed from the pool equipment industry, anyone with the ability to dig, make things level, and move rocks and dirt around can create a beautiful living water garden if they use proven equipment and methods.
Now I will admit that there are other ways that can work; But none of the other pond construction methods have the successful track record I've seen with pond installs using this system.
The basic elements for this system are underlayment, liner, rocks and gravel, skimmer, fill valve, pump, plumbing, biological filtration, plants, fish, and bacteria.
Here's a simplified explanation of how this works as an ecosystem. Fish eat insects and plants and then the fish waste spreads through the system . The skimmer draws water off the top layer of the pond helping with circulation and aeration while trapping floating debris in a net. The pump is situated under the net in the skimmer and pumps up to a bio-filter. The bio-filter is often designed to be incorporated into a waterfall. The water enters the bio filter and rises up through filter media that is colonized by bacteria. The bacteria converts the waste into forms less harmful to the fish and less conducive to excessive algae growth. The waterfall or stream add more aeration that the bacteria and fish need. The plants uptake more of the nitrogen and some oxygenate the water. The rocks and gravel provide more area for bacteria and protect the liner from UV rays.
Sheesh! Every time I set out to give a simple explanation of a pond ecosystem it still takes 10 sentences. Suffice it to say that all the parts work together to make your pondkeeping easy!
I use the word easy as a relative term. Compared to the work and rebuilding you may experience with other methods this is the easiest way I know. But there is still a good deal of work in pond construction. Obviously you need to dig and shape a hole in the ground and move some heavy items around. A well trained crew with everything needed on-site can install a pond in a day. It may take a few weekends for a homeowner to do the job himself, depending on their ability, time, and conditions.
Some key points:
Size: It's best to have it at least 6 ft across. Bigger is better. 16 x 11 is a good medium size. Generally people regret not making the pond larger when they are done with their first one.
Location: There is a tendency to put ponds in a place where water already collects in the yard. This isn't always the best idea. Groundwater running into the pond can create problems. If possible bring it right up near the patio where you can enjoy the fish and flowing water everyday.
Electric and plumbing: Don't overlook the need for a GFI outlet near the pump and a water source to keep the pond topped off. Most kits for some reason don't include a fill valve, but it really is important since on a windy day a pond can easily lose an inch of water. Left unattended this can lead to the pump running dry in the skimmer for a long period causing possible damage. The ponds level of course won't drop below the skimmer opening.
Lets go over the basic steps for installing this type of pond system.
Decide the size of the pond and order a kit with all the necessary components. Layout the shape of the pond with something like a garden hose. Leave it out there for a while, move it, think about where the falls and different plants will be. If you are building a stream do the layout for it too. Level ground isn't a problem since you will be excavating enough soil to buildup around your waterfall filter. Paint an outline with orange marking spray paint.
Make arrangements for getting the variety of rock and gravel you will be using.
Position your skimmer and BioFilter. The skimmer should be on the opposite side from the falls or stream to create circulation. Then lay the flexible PVC, or kink-free pipe between the skimmer and waterfall filter. This is so it can be covered during excavation instead of trenching it in.
Establish a firm compacted and level base for the Waterfall filter, perhaps leaning slightly forward, depending on it's design. If you have help they can be working on digging the pond while you get this right, or vice versa.
Hook up the plumbing to the filter and backfill around it. It's a good idea to have someone stand in the filter while it is being backfilled to prevent it from shifting out of position on the base.
Examine any slope of the land and establish where the water level will be; usually a couple inches below grade. Finish digging the pond relative to the water level. A rotating laser level is the ultimate tool for this, though they are expensive to rent. Patiently checking string levels in all directions can get the job done also. Include shelves for marginal plants and keep the sides and shelves level. The deep part of the pond should be around 2 ft or a little less. Any deeper and most towns swimming pool codes kick in with fence requirements. Unless you intend to keep a great number of koi this will be plenty deep for your fish. Planting pockets for water lilies can also be dug now. These pockets create a plantable depression in you liner for later. You can either plant directly in these pockets or hide your planters in them covering with gravel creating a more natural looking pond.
Excavate the position for the skimmer so it will be on a firm level base that gets it into correct position relative to the water level. Recheck everything. All the measurements and levels. Make sure the pond is free of sharp objects and unfold the underlayment into it. Start in the deep area pushing the underlayment into all the shelves and pockets. The EPDM rubber liner is then installed in the same way, making sure that it extends far past the waterline (settling will occur) and above the openings on your skimmer, filter, stream etc.
Add rock and gravel. Pre-washing the stones can help with a clean install or you can hose them down in the pond while pumping out the dirty water. Use larger stones at the base of each wall that forms a shelf, building up with smaller ones. Cover flat areas with 1"-2" gravel...absolutely no more than that. If you have extra gravel don't be tempted to just use more in the bottom of your pond. This is for biological reasons I won't go into now. The rock should have your liner pretty well pulled into position now so you can make final adjustments on your skimmer and attach the liner to it according to the manufacturers instructions.
Start filling the pond. Now the fun of building the waterfall and stream. Make sure you have plenty of slack running up to the falls opening before you attach it and make any cuts. Also take care to avoid folds in the liner as you twist downstream. Folds in the stream liner are a common source of leaks and why a very wide liner for a stream is recommended. Dry stack stones as in a wall up the front of the waterfall filter. Using black waterfall foam or some other type of expanding foam to seal the space between the rocks. This makes the water flow over the rocks instead of disappearing into the cracks between. Black waterfall foam is nice for blending in with the rocks. The basic outline of the stream should have been established with excavated soil from the pond, but some digging of different catch pools may be necessary and you may need to build up more of a berm at the waterfall. Rock in the sides of the stream and cover the bottom with gravel as in the pond. Use the waterfall foam to seal in rocks wherever a cascading effect is wanted, using flat rock to form the lip of falls and sealing under them.
Install the pump, install the overflow plumbing and fill valve in the skimmer. When water level is high enough and all the waterfall foam is dry, (you can assume your hands will be covered with the stuff, but try to avoid it because it is very difficult to clean off!) try out the pump. You will then need to refill the pond as it will take a large volume of water to fill the plumbing, falls and stream. Once you are happy everything is as it should be, cut the excess liner away. Leave several inches of liner for settling and possible adjustments.
There are plenty more nuances to building a pond but this should give you a decent feel for what a water garden project entails. The kits we sell include a decent installation manual and I'm happy to answer any questions as are many other pond enthusiasts.