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/Aquatic Gardens, Design, Construction & Maintenance

Example Systems: San Diego Technical Pond

By Bob Fenner

Breathtakingly beautiful

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon

by Robert (Bob) Fenner

World-class Japanese gardens all bear certain hallmarks; meticulous plantings hand cultivated to be pleasing in view from all angles; seemingly natural, perfectly placed rockwork; and water effects as a central element. Such is the case with this example "pond" smack dab in the middle of San Diego's "little silicon valley", Sorrento Mesa.

Originally conceived as an authentic part of a total Japanese building/restaurant and landscape, this site is now one of the Karl Strauss outlets here in San Diego. As with its changing use, the pond itself has undergone an evolution of its own; in filtration modes, as you will see.


The pond basin itself is at the center of a man-made canyon with a thematic restaurant adjacent to an edge on the south. This layout, with its expansive views of surrounding plantings, gives the viewer the perspective of looking out of an area not unlike a mountain meadow.

The whole of the landscape was dreamed up and executed by a Japanese master gardener some ten years back whom the author was honored to drive about to secure suitable types and sizes of rock. Though our companies did not do the construction, any of the follow up modifications, nor maintain the system, we visited it many times for its beauty (and proximity to our offices), and I was there for the presentation of landscape awards.

Most of the ponds sides are sloped to vertical, with one west-facing area gradually dipping as a faux beach/feeding area. Depth varies between 2-3 feet; the basin is approximately 60' long by 40 foot, though naturalistically asymmetrical. About 27,000 gallons by meter measure; due to its low level orientation there is relief from all but overhead the sun.

The surrounding landscape, plants & placement, is a mix of traditional (MANY large Japanese pines, put in as 24" boxes; azaleas, rhododendrons... as well as a Cal-style mix of junipers, mock orange, Indica hawthorne and a few nice nuances in the way of the bane of gardeners of the fifties, "Chinese yellow bamboo", and a giant variety.

The hillocks and rock walkways are an absolute delight; many paths leading to meditation and observation areas; changes of view and venue at every turn and angle. This is a large private garden that presents an even grander appearance.


This is a "production" pond of liner over dirt, chicken wire tied to a berm support of rebar, shotcrete with six sack mix and brownish coloring. Very little was done to modify the rough edge and rockwork in, around and over the edge and basin was placed before shotcreting. The effect is beautifully natural, and yields a nice, slip proof finish for human workers in the water.

The bottom, however, is unfortunately almost entirely flat, and this has proven to be a great liability in cleaning and emptying the basin as well as a "biological challenge". The resident koi carp fish life has nowhere to go to get away from avian pests and predators, or to behaviorally thermoregulate by swimming to water of a different thermal regime. A sloping area to a few feet greater (perhaps under the island bridge) would have been a good idea.

Filtration: was, also, unfortunately an apparent afterthought. The original plans (I bid against them) called for two 3-HP pumps to service three sand filters (Oh no!); these quickly proved inadequate; prompting the aquatic maintenance company involved to resort to toxic chemicals (killing the livestock a few times over). Good for fish and plant sales; bad for public relations. A second company/filtration generation was tried out incorporating several swimming pool type cartridge filters (with big sales of extra cartridges and cleaning gear for same) These don't work on biological systems (clogging daily) and were dismal failures. is and should be a chief concern in any water effect.

Skip ahead to present circumstances. There is an inadequate, over-driven (by flow-rate) biological filter composed of a single poly shipping container utilizing plastic screening for filter media. But huge money was spent on other high tech. gear. There is a huge protein skimmer (non-functional all the times I've seen it)aided in it's operation by a refitted ozone generator.


Livestock: There are about a hundred ornamental carp, aka koi, of mediocre quality due to genetics and upkeep, and a handful of resident mallard ducks. Aquatic and bog plants are blind-potted (no openings to the bottom) in black plastic pots. The plants are beat for the time of year and dearly need to be re-fertilized; once a year, on thinning and repotting, with slow-release fertilizer tablets.


Unlike the spotless landscape surroundings and buildings, the pond and its livestock show signs of woeful neglect. The fish show signs of beating, probably from the waterfowl, and there is a prominent algal scum that accumulates at one end via the prevailing wind.

A typical protocol for such a system includes weekly water testing, cleaning of trash and filters, a modicum of bottom vacuuming and water replacement. This time of year (winter), with water temperatures below 55 F., feeding is contraindicated.

Suggested Changes:

Those ducks: they've got to go. No matter how cute and eminently feed-able, waterfowl on a basin of this size and type are foul. Each one adds several ounces of manure per day to the system, directly contributing to poor water quality, algal proliferation and loss of fish vitality. Top this off with their propensity to thrash the aquatic and surrounding plantscape, and you can see... they're destructive beyond salvation. Get rid of them.

Filters and Media: The amount and type of filter surface area for a system of this size and kind, with or without ducks, is ridiculously too small. Standard operating procedure calls for filters of at least ten percent of the surface area of the water itself... plastic shade cloth material? Not a good idea for filtration capacity or ease of cleaning. An in-basin filter adjunct or finely tuned fluidized bed requiring much pumping expense are about the only viable alternatives at this point.

Plants in the water: Need to be increased to cut down on both the amount of nutrient and light available to undesirable algal forms. Trays of unpalatable hornwort, aka Coontail (Ceratophyllum demersum)would be my first choice, grown in the principal basin and the enlarge filter areas.


This system gets an absolute A+ in terms of design and construction... except for its filtration concept for its intended purpose. In southern California, with high mineral content, warm, sunny weather and a lack of water depth, algae and other management problems are to be anticipated and avoided in advance. The San Diego Technical Center has too consistently shallow a basin, ineffectual filtration and DUCKS (!).

Bibliography/Further Reading:

Fenner, Bob & Rick Aspray 1983. Ornamental fish ponds. Filters: design, construction and maintenance. FAMA 6/83.

Fenner, Bob 1988. Water Effects: size and shape. FAMA 5/88.

Fenner, Bob & Matt Tsunoda 1988. Waterfall construction. FAMA 11/88.

Fenner, Bob 1988. Aquatic Gardens: Plumbing. FAMA 12/88.

Fenner, Bob 1989. Pumps: An introduction. FAMA 1/89.

Fenner, Bob 1990. Upflow filters (for biological ponds and multi-tank systems). FAMA 2/90.

Fenner, Bob 1990. Pond construction: (Processes in) Building concrete and liner (production) ponds. FAMA 9/90.

Fenner, Bob 1991. Thorosealing cementatious water features. FAMA 5/91.

Fenner, Bob 1994. Pond construction methods. FAMA 5/94.

Fenner, Bob 1994. Concrete and block construction of ponds. FAMA 6/94.

Fenner, Bob 1994. Filter media for ponds: A discussion. FAMA 8/94.

Fenner, Bob 1993. Electricity and electrical use around water gardens. FAMA 12/93.

Fenner, Bob 1994. In-pond (versus outside) filtration. FAMA 9/94.

Fenner, Bob 1995. Selecting a site for your outdoor water feature. FAMA 5/95.

Fenner, Bob 1996. Plants and planting for water gardens. FAMA 6/96.

Fenner, Bob 1996. Surrounding landscape plants for your aquatic garden. FAMA 9/96.

Fenner, Robert M. 1997. Aquatic Gardens; Designing, building & stocking a backyard pond. Microcosm, VT.

Graphics Notes:

and 4) Details of the island feature, joined to the land by way of a bridge (note: not Chinese red)

5 and 6) Views of the numerous stone-laden footpaths. At several points there are "meditation" areas offering a closed path, bench and tranquil view.

7) The pathetically inadequate filter box (poly tote of nominally 4 by 4 by 3 feet size), filled with shade cloth for biomedia! A pond system of this size, type, with so much animal life in it requires about ten times this much filter. Ridiculous.

8) In the refitted pump vault, a gargantuan modern RK2 protein skimmer, with an ozone and automatic wash down system. There still is a need for more bio-filtration.

9) The state of the aquatic plants (bad) seasonally is obvious. They're in dire need of repotting, and fertilization... after the waterfowl are removed.

10) Mere evidence of eutrophic conditions. Duck manure, overfeeding, inadequate biological filtration... what does it all add up to? Algal proliferation. Here is one of the worst types, surface scum. This green goop not only will outcompete the desirable vascular plants for nutrient, but block out sun to the life below.

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon

by Robert (Bob) Fenner
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