I think most of us have flexible liners like EDPM (roofing liner) rather
than pvc...it does not last well. It is easy to install and does not
crack as brick and cement can. It is cheaper than cement.

Phyllis and I have a cement main pond (2,900 gal about the size you are
intending, 2' deep, with an old spetic tank in the middle providing a 7'
'deeep well') and EDPM in the berm ponds. The big risk of cement is
cracks, even if you waterproof the inside. Ours is in-ground, so brick
would not work. The concern about brick would be cracks at the joints.
Solid cement is essentially a slab.

We used a very strong cement and rebar at 12" intervals. The cement is
5" on the bottom and 6" on the sides. It was a bear to pour and smooth
(did that ourselves).

If you do the sides and bottom in two pours, you have to put an
effective sealant between them to handle leaks at the joint. We used the
tar-like strips that are used in commercial buildings. The strips are
about 1" and lay next to the rebar from the bottom up into the sides.
You pour right over them. If water gets in, they swell up and seal the
joint.

sides, cement will hold its own weight after about 1/2 hour of
setting, your side forms can be a bit weaker if you do the walls by
circling the pond pouring a foot at a time instead of all the depth at
once. We put the drains, etc into the cement. It is now 10 yrs old and
no cracks.

Good luck if you go this way.

Jim

Danny wrote:
Ive been reading up quite a lot about building fish ponds & water gardens &
what I see is that they all advocate the use of PVC liners for lining the
pond. Nobody talked about using bricks & cement or mortar. I'm actually
planning to build a fish pond measuring about 18'x20' in my garden and I
plan to build a more permanent structure by using bricks & cement and
subsequently after plastering, applying it with waterproof coating. Besides
the cost aspect and probably the acidity problem which could quite easily be
cure or neutralized, what are the other disadvantages or adverse effects
that could crop up ? I have in fact constructed the bio-filter & waterfall
with bricks and wandering if it would be disastrous to continue with the
main pond the same way. Appreciate your expert advice before I proceed
further. Thanks all.

Regards,
Danny