When my city was hit by a tornado in 2011, my summer overflowed with balancing my full-time job with lots of volunteering. When the dust finally began to settle in late summer, I wanted to get my hands dirty and create something peaceful in my garden space- so I built this above-ground koi pond! Unfortunately, 2011 was before I began taking photos at each step through my projects, but I’ve attempted to explain the process here in detail so you can make your own above ground pond.
This is very easy and very cheap- even I was surprised at how well this idea worked! Using shims, I was able to create my pond on very rocky, uneven ground. As long as the top of the wood frame is adjusted to be level, the water level will be even and adapt around/over natural landscape. Best of all, unlike other garden pond projects, there is absolutely no digging involved! I dismantled this pond in late 2015 and repurposed the materials, but even after four summers and winters, this pond was structurally sound and leak-free.
- cordless drill (Electricity and water don’t mix! A small cordless drill can complete the project without dangerous voltage)
- a level
- galvanized screws (to prevent rust)
- Raised Bed Corner Brackets – I used hinged brackets which no longer appear to be available, but if your pond will have corners that meet at 90-degree corners, these steel brackets should be stronger and more supportive than hinged ones. NOTE: Don’t cheap-out on the brackets. They need to be strong enough to support the wood planks that bear all the outward pressure of the water (and that’s a lot of pressure!).
- 2×6’s (pressure treated)
- Furring Strips (small boards that can be screwed along the narrow side of a 2×6)
- Pond Liner – You’ll need a pond liner that matches the dimensions of the raised bed you build + extra for the sides and additional overhang just in case. Use an unprinted advertising billboard tarp for a UV-protected, slightly less expensive alternative.
Step 1. Build a Sturdy Raised Garden Bed
First, create an above-ground frame for the pond by constructing a basic raised garden bed using pressure treated lumber and raised-bed corner brackets. Don’t use a flimsy set of raised bed brackets- they will need to be strong to support the outward pressure of water. My pond was built on a slight hill, so 3 sides have stacked 2×6’s while the highest side has only one board.
Leveling your raised bed isn’t technically necessary, but if you want a waterline that is parallel to the top edge of your boards, you’ll need to pay attention to high and low edges. You may choose to dig an inch or two to set the boards on one side lower, or just use bricks or shims to lift the boards of the lower side.
Step 2. Acquire Pond Liner and Test Water Fill:
Next, you’ll need to find something to use as a pond liner. Commercial pond liners are easy to find and nice because they are low maintenance, but for this project, I managed to find a used advertising billboard tarp for my pond liner, helping keep my project cost very low.
Spread your liner over your raised bed, with at least 3 ft of material overlapping over each side, and use a hose to fill the pond about 1/3rd of the way- just enough water to weight your liner down into the frame. STAY CLOSE while the water fills and help manipulate the liner to help it sink evenly and neatly to the bottom.
As it fills, you’ll need to create folds to make the liner accommodate the sharp corners of this pond design. This is easiest done with only as much water in the pond as is absolutely necessary to weight the liner.
If you want to be able to drain your pond (as opposed to pumping-out for cleaning) pause here check out my article on using plumbing fittings on either side of the tarp/liner to create a drain connected to a hose with a shutoff valve.
Step 3. Fill and Level Pond:
Continue filling. The rising water level will inform you how well you leveled your sides. Use shims to make slight corrections by lifting corners or adding space between sideboards.
Step 4. Finishing Sides:
At this point, you’ll have a functional pond that looks a little more like a redneck kiddie pool than a relaxing water garden! Never fear, the next step makes an enormous difference. These final steps neaten the overlapping liner and provide a finished edge:
I recommend completing this step with the pond filled completely. Although you’ll probably get a bit wet, the result of finishing the edges with the liner fully weighted (as it will be when it is in use) is the best way to ensure the correct placement (and accordingly, the longevity) of your liner.
Steps to Finish and Neaten Sides:
- With the pond filled completely, go around the perimeter of your pond, cutting the liner like a pie crust (keep enough excess to let the liner drape over the edges by about 6-10″ on all sides). This first step just removes bulk to make the final steps easier.
- Pre-drill holes in the furring strips and place over the top of the first 2×6, sandwiching the liner between board and furring strip. Pull the liner taunt on the outside and then use a cordless drill and corrosion-resistant screws to screw the furring strip down, pinning the tarp between the furring strip and the 2×6″ retaining wall. (Yes, screw through the tarp.) Add 1 screw every 12″ to securely hold the tarp edges in place. (Note: According to Google, which may or may not be reliable, using a small cordless drill in or around water is not an electric shock risk, but NEVER use a corded drill while standing in or around your pond!)
- Continue around the sides of your pond, taking care at corners to fold and tuck excess tarp material.
- Once the furring strip board is added on each side, use a sharp knife to carefully trim any tarp edges showing on the outside of your pond.
Once the sides are finished using these final steps, you have a complete garden pond ready for koi, water features, or aquatic plants for only the cost of lumber, brackets, and a tarp! You can create an endless assortment of water features by adding pumps, troughs, and raised vessels to your pond.
Maintaining an Above Ground Pond Year-Round:
Maintaining an above ground pond in the winter can be a challenge. You may choose to drain your pond- although if your pond supports fish you may want to try and keep your pond partially thawed all winter to help your pond fish survive and grow larger.
An above ground pond will freeze more quickly than in-ground garden ponds, however in zone 6 I have successfully overwintered ordinary goldfish even in exceptionally cold winters with sustained temperatures below 10 degrees F by keeping water circulating with a pump and by providing insulation in the form of a filled 100 gallon trough sitting on cinder blocks in the water. The combination of insulation and moving water has produced hardy fish that thrive.
You may wish to purchase a commercial pond-deicer which will maintain your pond at just-below freezing. See also our article on using compost during the pond-building process to create a self-heating pond.
Edible Gardening in a Water Garden: Growing Watercress
It’s easy to turn a backyard water feature into a productive element in a vegetable garden. I’ve had success growing strawberries in a floating planter, growing chickweed around my pond, and particularly in growing watercress in my water feature. Watercress grows best in cool moving water and needs no soil- in fact, the copious and thick root system works as an effective natural water filter when grown in a garden pond (but, unlike other aggressively growing water plants, watercress will die back fully in the heat of the summer- requiring little to no maintenance controlling it)
To grow watercress in your garden’s water feature, you can buy starts at the grocery store or farmers market. (You do want to be careful to be sure and purchase true watercress, though, not “upland watercress” which has a very different growing pattern and won’t thrive in a water feature) Once you have shoots of watercress, you can easily root the shoots in your water feature by securing the shoots to a stable area so they won’t be caught in your fountain or filter. Even if the watercress doesn’t have significant roots still attached, placing the sprigs in a nutrient-rich environment of moving water should ensure that rooting occurs quickly.
How to root watercress in a Backyard Pond:
I use metal hardware cloth (aka small animal cage wire) to hold my watercress in place near my pond’s waterfall without allowing the watercress to flow over the waterfall. I take the new watercress each spring and place each sprig securely through an opening in the wire mesh. Simply holding it in place for a few days will be sufficient to let the roots begin to grow and intertwine with the mesh- at which point you’ll find it difficult to remove the watercress from the hardware cloth!
When growing watercress in the early spring, it is prolific and grows in large masses far earlier in the growing season than other vegetable garden plants begin producing. Using this method, you can help your backyard garden pond contribute to growing edibles in your garden. Watercress can be harvested continuously for salads, sandwiches, and snacks from early spring into summer, providing effective, natural, and chemical-free filtering for your backyard pond in the process.