Steven Williams
- please send us a sketch of the space. Where are the current building walls, where do you want the pond etc.
From your pictures it looks like a nook in the building with 3x walls surrounding - perfect. You might be able to simply run concrete blocks around the square, dig a bit of a belly in the middle & for drain-plumbing & sling poly pond-liner between & over the blocks to seal. Even a full-grown aro won't need more than 24" depth (though more is better) so not much digging necessary and bring depth to a few inches below window. Note: You could just set a rim of timber around the walled edges & sling the liner from that, but it's never advisable that water share a structural wall (without professional oversight)
I would agree with whoever suggested a glass front. One row of block, then set the glass/acrylic to the intended surface level & over.
Re. jumping: expect this will happen. However, on 3x walls it won't, and the 3'd wall is already glass/acrylic. Either make the glass pannel taller, or stop it at the intended surface & run a thinner/cheaper piece 3~5' above that. Or a mesh, though that'll be ugly.... Somebody in Thailand had a fantastic set-up posted on here a few years ago; an all-cement wall-build pond with glass front & side that extended 6' high. Anybody remember?
Plant surface lilies into pots and set along the wall edges, particularly where you're worried about jumping.
Yes, do introduce guppies to reduce pest-possibilities, general tidy-up and/or a splash of colour. Your fish should nearly be big enough now to not see them - guppies are wee. Alt might be to go with something smaller again, as even the smallest tetra, ricefish & killies will eat mozzies.
Koi will make a mess & eat your plants. Try to stick at the top (aro) & bottom (tetra, snail, cherry shrimp) of the food-chain, as overlap gets complicated.
Where is your filter going to be? Could be all submerged; you seem to have the acreage.