trev i think its great idea
my koi pond is fiberglass-and rather large-like 1200 gallons! in the ground
i know this isnt what youre thinking of
here are some thoughts from my experience
first make it thick, use lots of reinforcing fibre web-dont be cheap in materials, make many layers-id say at least 5--you might wish to use wire mesh -install into your framework -support-then cover with fibreglass
-thin will crack like and egg-thick will last decades, make it have a flat bottom (?? makes so you can sit things in it-like a plastic plant-rock etc) and in your case-it is likely to need under supports
if you like-find water proof paint and graduate color-ie very dark at the bottom and lighter toward the rim-and the rim should be curled a full 180 degrees for added rigidity to the side - unless you use rigid support and this isnt an issue
if i might, dont add sand-heres the concern-
water features grow stuff-a smooth surface is easier to clean --otoh-since yours is more a model in style than a real living pond -you might give it a go-its just that fibreglass is rather expensive to experiment with -i think a careful paint job will take care of things-or you could use sand around the top 3-5 inches-
consider too
possibly a shelf around the edge for unerwater potted plants- ?? -dont know if this a consideration-but it can add real life to an otherwise static feature
some other thoughts
water features are fun- and-to keep things fresh-you mightl want a pump to circulate water-better still -a small fountain (??-even a mere burble to the surface to keep water moving a bit) maybe not in your case -this aerates the water, keeps the water much cleaner (natural UV and air tend to keep bacteria down) -
they must be dead level -the rim i suggest looks not so great but is forgiving in this regarde aompared to a flush mount
-large retailers that sell garden stuff often have ready made black plastic pond fits-terraced, pump, sometimes lights-these seem a very easy way to try a pond and look like it might do the trick-whether you can get them to look/size integrated and natural is a question-but water features really can be a joy-underwater light(s) can really bring them to life as a night time garden /patio feature
it is difficult to get real water to look real on a small shallow install-painting will be critical to give the illusion of depth-ie shading
just some thoughts
