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/Aquatic Gardens, Design, Construction & Maintenance

Pond Profiles: The Phillips' Pond, From Swimming Pool to Biological Modification

By Bob Fenner

Overview of the Phillip's Pond

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

The Phillips' are a delightful retired couple with a completely self-designed, personally overseen home. Mr. Phillips made his well-earned fortune by "doing custom cabinetry" for resorts, casinos and other well-off folks, and Mrs. Phillips is a gardener extraordinaire. Among other positive characteristics this all adds up to the fact that nothing was left to guesswork in their living space, including their "fish pond".

However, though the original system was engineered and constructed by competent landscaped architect and construction outfits, it was not well suited for it's ultimate purpose, a combination lily and koi pond. Let's take a look at what the Phillips' first had built and how our company aptly modified and replaced parts to optimize it's function.

Design & Construction:

From the get-go this pond system bore much more resemblance to a swimming-pool than an intended biological system. For construction, this is/was not necessarily a bad thing. The single lower basin is about twenty five feet long and eight to ten feet wide, with a nominal depth of three feet. Unfortunately it only gradually slopes to a central drain, and it's intake skimmers can be death traps to small koi. A double-edged sword is the beautiful black-colored cement plaster coat that seals over the Gunite and re-bar shell. On the one, it looks good and is easy to brush clean; on the other, it's a deadly slippery surprise to even the nimble footed. Best to stay out of the pond.

The pond is about 7,000 gallons counting the smaller upper falls/basin (about 10 by ten by two feet).

The sides of both basins are pretty vertical, with a gorgeous mix of rocks interspersed around a bull-nose brick perimeter; very striking and a mix of formality with nature.

The pond faces due east and is in the very front of the house, with a walkway over on its way to the front door. On real problem came about as a consequence between their neighbors shared fence and property line: pump noise. More about this below.

Plumbing:All's well here, plastic (PVC) or proper diameter and pressure-rating, with one exception. The system had a deadly flaw, an in-line (with other discharge plumbing) fresh water make up valve. More than once, this line was manually left open resulting in a disastrous loss of fish life.

Filtration: On my first visit to the home, this was my first real misgiving about the pond'¦ for biological purposes. The pumps utilized (two Sta-rite MaxiJets, one a two-speeder), plumbing, electrical, even the landscape-matching enclosure were all top-notch work'¦ but not for the intended purpose.

What sort of filtration did the system have originally? A D.E. (Diatomaceous Earth) filter; great for swimming pools and spas with very little solids and sanitizers (like chlorine) to keep algae et al. critters at bay. For the uninitiated D.E. filtration involves finely meshed cartridges whose sleeves are coated with a slurry of siliceous skeletons (long-since dead diatom algae) and high pressure water pushed against it. Quite small (about 0.1-1 micron particles are trapped, otherwise excluded from getting through. For living system with all sorts of bio-junk in them, these filters clog pronto, requiring daily or more backwashing and refitting with more D.E..

We were called onto the scene as a company as a matter of fact to offer our suggestions of how to remedy the lack of effective filtration caused by the inappropriate mode being employed. Our suggestion and ultimate action was multi-pronged, and is detailed later.


Livestock: Ornamental carp, aka koi, and some very nice waterlilies in plastic pots (fitted with koi-proof plastic net screens over their media) make up the macro-biota of the system. The plants are fertilized once a year, on thinning and repotting, with slow-release fertilizer tablets. The fishes are fed excellent quality white fish meal based pellets, twice a day when the water temperature is over 65 F., once between 65 and 55 F and none when lower.

Maintenance: Besides regular periodic water changes (once a week or so in summer, to once a month in winter), Mr. Phillips utilizes a gravel vacuum and a "wash-down" procedure to break up the gravel in the bio-filter, preventing clogging and channeling.

Changes Made:

Filtration: As alluded to above we built a massive bio-filter with Mr. Phillips help in the upper (falls) basin. In essence, a wall was made in the top of the discharge that directed water under a substantial screen mesh supported by brick. Water and debris does a reverse flow path through a good 18" of 3/4 inch graded crushed rock, and overflows a further wall before plunging over the original falls. ( See Schematic Illustration).

A feature of tremendous utility is a drain that allows for dumping the upper basin alone; very handy during regular cleaning.

In order to provide for maximum biological cycling and surface area, we removed the D.E. filter sleeves and packed the stainless filter body with plastic bio-media.

The pumps we left as is, because they're more than adequate for circulation (the single two-speed runs continuously on the low, 1/4HP setting, the higher is turned on to impress guests, the other pump is kept on reserve-back up). Styrofoam insulation in thick sheets was annealed to the pump vaults walls and the adjoining landscaped beefed (leaved?) up to placate the neighbors.

Lastly a multi-bulb TMC Ultraviolet Sterilizer was installed to improve water quality. These are great units that come stock with quartz sleeves, a remote able ballast and 1 ½" fittings. The UV helps reduce water borne algae to a minimum, increases RedOx and dissolved oxygen'¦ all good things.

Plumbing: Eventually I got my way and permanently secured the potentially deadly make-up water valve. The problem with small koi getting into the skimmer intakes was solved by simply procuring larger fish.

The Future:

Re Pump/pumping: If/when those Sta-rites finally go, I would encourage the Phillips to switch out to a pump and motor combination that produces about the same gallonage, but at substantially less pressure (the swimming pool ones are intended to provide both volume and pressure). This will save considerably on electrical costs.


When first asked what might be done to clear this system from the drudgery and expense of daily (or more frequent) D.E. filter cleaning and suspended algae, my response was to do parts of all that was eventually done. The size, shape and quality of construction of this effect were/are all A+'s, all that was really necessary to make it a biological system was to get rid of the swimming pool/spa filter, install adequate bio-filtration and add the livestock.

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. FAMA6/96.

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

Fenner, Robert M. 1999. Aquatic Gardens; Designing, building &stocking a backyard pond. Microcosm, VT.


1,2) Two views of the bigger side of the main pond basin and the waterfall.

3) A view back down from the upper/falls basin that was modified into a sizeable bio-filter.

4) A graphic showing the principal features of the modifications done to the upper basin to make it into a biofilter, utilizing the existing pumps and plumbing.

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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