pond with brick wall

Hi,

Im thinking of building a pond. I am going to build a brick wall in a
sort of shape like this looking down from above (well not quite that
shape but u get the idea.).

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The wall we be about 3 feet high from the ground and then I will put
decking around at I expect about 12 inches from the ground. So I will
see 2ft of the wall above the decking. Then fill inside the walled
hole with 1ft of soil, then lay a rigid pond on top of the soil and
back fill it all in. Then stick some plants (ones that dont drop
their leaves) in the soil that is around the edge of the pond.

I will put some goldfish in the pond so will put in a filter/pump etc.

Does this sound reasonable to you?

Will a wall one brick thick be enough support for all the soil and the
pond.

Ive heard of retaining walls - ones that sort of click together - like
lego:-) Would this be stronger?

Im still reading up on depths of footings etc as the idea is at its
very early stages.

Im a bit concerned about the soil I put under and around the pond
shell. It will have to be new soil delivered to me and as such may be
quite 'light'. So Id need to compact it down. What I dont want is to
compalt it as much as I can and then find within a few months the
weight of the pond compacts it even more and the pond sinks?

Any tips for how to avoid this, eg type of soil or how to squash it
down?

Also any gotcha's I need to think about.

Im a novice at brick wall and pond building although not too bad at
indoor DIY jobs. The house is all complete now though so I need a new
challenge.

TIA,
Scott