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/Aquatic Gardens, Design, Construction & Maintenance

Fiberglass/Resin Ponds

by Robert Fenner 

Can you tell what this pond is made of?

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

Fiberglass and resin ponds, whether pre-formed or made on-site are a controversial means of construction. Proponents vigorously promote then as fast and easy to install and relatively low cost (compared to concrete).

On the downside, the negative argument; the active ingredients, their application and degradation products are toxic (!), the pre-formed ones are generally too small, shallow and not practically-shaped. They require more and careful care compared with liner, concrete and other pond-making technologies.

Made-on-site fiberglass and resin projects fare little better than pre-formed; they are a nasty mess to produce and like their pre-made counterparts must be conscientiously protected from weathering and not stepped into (they fracture).

Back to their saving graces; fiberglass/resin ponds can be easily moved, replaced and repaired. Especially for folks who aren't quite sure what they want, if they want it, and how long they want whatever it is, fiberglass/resin, henceforth designated "F/R" ponds may well be the most appropriate methodology.

What the? Upside, Application/ Preformed F/R Ponds:

Where do you become familiar with F/R possibilities? How can you find out more? Check out the hobbyist bulletins and magazines' ads; take a look inside water-garden outlets and mail order catalogs. Survey the "yellow-pages" under Fiberglass Fabricators in your area. Visit around and you'll see a multitude of preformed fiberglass/resin offered and made to order. Some are even modular! Enabling the arrangement of placing one spilling into another. Matching pre-made faux rocks, waterfalls, streams and filters can be had as well.

A further elaboration are multiple piece bolt-together models that allow the owner to design their own shape. These are arranged, fastened and siliconed together before being installed. Which brings to mind an important element of their cost:


If you're having a pre-formed unit shipped across, between countries, or even just across town, be aware that the dollars in transit can be considerable; possibly the largest expense of the entire enterprise. Check this out completely; drayage to the site and getting the pond(s) to where they're going in can be a major affair. They're heavy, bulky and subject to fracturing if dinged or dropped.

Shape & Size:

The larger and more steep-sided your pond basin(s) the more stable and easier to maintain the system will be; regardless of what it's made of. Many F/R ponds are too shallow, gradually (saucer-shape) sloped, too little and with too-small nooks and crannies to be useful. Koi and other livestock have a tendency to launch themselves out of such configurations when they get spooked or excited.

Therefore look for and choose or build basins that are deep and steep and large as possible/practical. In my opinion (isn't that what all this is?) anything under two feet in depth and a thousand gallons is to be avoided for practical purposes for Koi keeping.


Pre-made ponds are almost as easy as liner-types to put in. Steps to completion include:

1) Design and Engineering: What are you doing, what for, what type of filtration, where are you going to put all this stuff, what the heck, over?

2) Siting: Usual considerations; e.g. significant-other inter-rator agreement, electrical, plumbing...

3) Excavation: Slightly oversize a few inches to make room for nesting material (usually sand) and conduits.

4) Fitting and Laying of Conduits: for plumbing and electrical.

5) Backfill: with nesting material, usually some type of sand.

6) Set in Pond Basin(s): Check and adjust for level. Pack in nesting material around perimeter. A 1 1/2" schedule 40 PVC pipe and tee makes a good tool for packing as you or a friend shovel in the sand.

7) Hook up Mechanicals & Controllers: Clean and fill up, fire over, check for leaks/performance.

8) Now and only now complete the decor. Rock, plantscape, etc. as in step 7) you may discover you'll have to break, dig up, and re-do part of the install. Believe me here or your temper may possess you to convert that intended pond into a guinea-pig raceway.

Grow Your Own? Custom, Made On-Site F/R Ponds:

Alternatively to pre-mades, folks with expertise, gear, wholesale access to the same might consider building one of their own in-place with chopped or layered fiberglass coated with resin. Special Steps To Completion:

1) Starting after excavation, you'll lay in conduits, painstakingly tape, cloth, otherwise mask-off their ends to prevent gunking them up.

2) Either apply fiberglass with resin via chop-gun technology (a technique that involves a pumping/shooting machine that chops up fiberglass and mixes it with prepared resin mix) or hand lay and over-lay fiberglass cloth and strip within the carefully dug basin(s) and

3) Apply the resin, hardener and possibly coloring via brushes you don't like>>> Let's stop right here and talk about safety. This stuff is semi-bad-news to get on and in you. you must wear protective gear; clothing, gloves, preferably a respirator (I'm serious) when doing these applications. Avoid physical contact and fumes (good luck). Peel off and toss the clothing and gloves after use.

Back to the schpeil at hand. Continue brushing the resin into the fiberglass matrix till the matrix is completely wetted.

4) Allow the entire project to 'set' an extra day beyond the resin manufacturer's suggested interval. This will vary depending on the type and quality of the resin used. Be aware there are vast differences in these. Coating and laminating resins are superior to "casting" types.

If you are purchasing large quantities of resin, etc. don't be shy about haggling for a discount. The price varies like and with the cost of oil... Also, purchase extra construction supplies with the understanding that if you don't open some cans/bags you may return them for a full refund; because all the resin work should be done at one setting.

Regarding Hardener:

Read and follow the directions on the resin containers thoroughly. Make a correction for the day's temperature and sunlight (if you can't shade the work), and shy on the low side of hardener use. That is, use the least recommended drops in suitably small batches. You want a slow, low temperature set, even if you're using a "hot-coat" type of resin.

5) Hook up the gear, test out and finish the aqua- and landscape as per pre-formed ponds.

6) Fini! & now my version or prejudice of what's wrong with this picture:


If my personal bias hasn't shown through (no duh!) yet, I'll admit it: I don't understand why anyone would put up with all the dangers and limitations of fiberglass/resin water feature structures. Pond liners are easier to install, modify, and remove, are non-toxic; and they cost less! Let's review some more of the negatives that are fiberglass/resin ponds.

Step On It; No! Don't Step On It:

Concrete reinforced (artificial) fiberglass boulders, borders, fiberglass filter bodies and basins have the same problem- they come apart; and the fibers stick in your livestock and you. Even if you construct a continuous protective border and cover well with gel coat or other sealants, they all eventually fail. One sure advocated maintenance activity is regular resin-re-coating of the structures to slow delamination and fiberglass shedding. This is a good idea for F/R filter bodies as well.

Once the system is installed, never step on the edge, walls or bottom(s), even if they're well shored with wood or other foundation. These surfaces are very slick; besides, you run the risk of breaking/fracturing the fiberglass/resin. Yes, they can be patched, but they will never be the same as first made.

Another operational concern is scrubbing down the sides. As you might guess, don't scrub!

I wish I could describe here the hyperplasia I've seen in the gills of necropsied ornamental carp that have apparently suffered painful deaths as a consequence of fiberglass fibers getting loose in their ponds. Ouch!


Have I talked you out of a fiberglass and resin construction or into building over an existing one? Good. If your heart and mind are set on this technology, keep looking... It's not cheap, easy, long-lasting or biologically appropriate. If you have a F/R pond for breeding, raising or treating, treat it gingerly.

Though I am a fan of discoursing, waging persuasive arguments for or against any given topic or concept, I would not like to take the pro fiberglass/resin side of a discussion. You don't have to dig as big a hole as for concrete or block types. They're more free-form/naturalistic? There are simply better technologies.

Bibliography/Further Reading:

Anon. Yearly. Installing your fiberglass pool. Lilypons Water Gardens (catalog), Texas, Maryland (800-999-5459)

Case, Deena B. 1986. The Fiberglass Experience. Practical Koi Keeping, Vol 1. Associated Koi Clubs of America, 1987.

Schleser, Dave M. 1975. Construction of a fiberglass fish pond. The Goldfish Report, Goldfish Society of America, May, 1975.

Wieser, K.H. Undated. Installing a pre-moulded pond. Aquarium Digest Intl. #43.

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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