Many pond builders are now exploring ways to combine technologies and techniques from the koi pond world with the water garden domain to create what are often called hybrid ponds. While there is no singular definition of what a hybrid pond is, it clearly is neither a conventional koi pond or a traditional water garden.
What is common to these ponds is that they are deeper than water gardens, averaging around 3′ in depth, but use water garden style skimmer boxes and/or filter falls filters in the design. Beyond that, the variables are numerous. Some designs include external filtration, external pumps, bottom drains, clean sloped bottoms, straight side walls and mortared stonework in a variety of combinations.
The goal in all of these designs is to optimize the environment for keeping koi. Deeper water helps protect koi from predators, since it is too deep for animals such as raccoons to wade in for lunch, and deep enough for koi to avoid predatory birds such as herons. This is not to say it is predator proof–just better than a shallower pond.
The deeper water also stabilizes the changes in the water temperature; changes are minimized because the water at the bottom, provides a buffer of cooler water to mix with the sun heated water on the top. Deeper water also provides valuable exercise for the koi, as they swim deeper and back towards the top. The water pressure in the deep water is said to help keep koi from getting obese.
Finally, a deeper pond allows a great deal more water in the same footprint, which dilutes toxins and helps slow down all changes in the water.
I recently got a call from Eric Tripplett, the Ponddigger, telling me he was building a hybrid pond for the winner of a contest he had held and he invited me up to take a look. Fortunately the pond was within easy driving distance, and he was building a hybrid pond, so up I went.
The pond fits tightly into a small backyard, tucked between a covered patio and the backyard fence. It is an upgrade from a previous pond, built in the same spot, so the koi were housed in a separate container for a couple of weeks while the pond was being built. That was one of the criteria for the contest.
The new pond is just under 1000-gal and nearly 3´ deep. It features an external pump, UV, air blower, skimmer, back washable filter falls and a pressurized bead filtration system. Once the pond was deepened, a bottom drain was placed and the liner dropped in place. The crew worked carefully to eliminate wrinkles on the bottom since this was going to be a clean bottom pond. Once the wrinkles were smoothed out, they added enough water to keep the liner in place. The sidewalls were vertical, and large rounded boulders were brought in and mortared in place with tan mortar.
The guys carefully filled all the gaps between and behind the rocks, working a row at a time, to allow the mortar to set up enough to support the weight of the next row of rocks. All the while they kept exposed concrete to a minimum with careful cleanup. I noticed they all wore latex gloves, which was smart, since a day of concrete work can wreck your hands for days otherwise.
On a job this size they did not use a mixer. They mixed the pre-colored mortar mix as they needed it, with a beefy drill powered mixing paddle in a 5-gal bucket. The final step was cleaning the excess mortar off the rocks with a large sponge and water.
Included in the crew was another customer who was planning his future pond and wanted to get some experience in the pond construction. He happened to be a part-time volunteer firefighter. As the crew discussed how they were going to move some of largest boulders into place, he went out to his truck and brought back a man lift. This bright orange tarp bag like device was very sturdy and had strap handles all around, so the team tested it out for moving the largest rocks. It proved to be an interesting device, and once everyone learned how to work together, the rock moving went well.
Easy affordable maintenance was a key desire for the homeowners. Thus, the design includes a bottom drain and no gravel so there will never be a need for a pond clean out. The filters are back washable, so it is easy for the homeowner or a service company to do regular maintenance. This is an obvious trade off against the beauty of river rock on the bottom.
Eric told me he now offers three kinds of ponds to all his customers–the water garden, the hybrid pond, and the koi pond. He explains the benefits and limitations of each, and has found his customers are very satisfied with the results.
-Backflushable Waterfall Filter
-Fish Safe Skimmer
-80L Air Pump
-75 Watt UV
-3500 External Pump
-45 Mil EPDM Liner
-LOTS of PVC Pipe & Fittings
Living Water Solutions
-Custom 3% aerated Bottom Drain