It is actually not a pond liner. Its a standalone, above ground pond made from MDPE. It does not need support. You can place it directly on a flat surface, and that's it. They also sell them here as potable water containers up to several thousand litres sizes, very sturdy and they also have 10 year guarantee. If I had more space, I would have bought one with a larger diameter. I live in Europe, so you many not find the same but if you are in the US, they sell round fiber glass tanks which I couldn't find here. I think the round shape is really a key to the fish. I think they're really, really happy in that shape. They think its an infinity pool swimming the perimeter
The lights I am using is one kessil 350W, which is the one right above, and one 30W Flood light which only illuminates the tall plants out the back. When just the flood light is on, the clown loaches have a party

They like having some light but not too much and it just gives them that "dusk" type of illumination they like
The tall potted plants are peace lilies, parlour palm and a fern I forget the name of(common one), but all do great with wet roots. They are planted in baskets with just hydroton clay pebbles. It works best as it gives water flow around the roots.
There are potted plants under water too. I use a layer of hydroton clay pebbles, a layer of plain top soil, capped with small gravel. The pots need to be sturdy because the clowns knock them otherwise
I do not cover the pond at all. I do not fill it right to the top. The water level is about 10cm below. It needs a really determined fish to make that distance... The pond also has a narrow lip around. No jumpers so far. Its been set up for nearly 6 or 7 months now. All fish I have are advertised jumpers, SAEs, denison barbs, kuhli loaches, and the clown loaches....two of which did jump out while in quarantine in the past...in a small open top tank..
I think jumpers has to do a lot with too big fish or too fast fish, in a too small tank or generally small tanks where fish feel threatened easily. I've had several jumpers out of my small tanks, same fish never jumped out of a big open top tank.... My clown loaches have been in an open top tanks for the last two years, and previously in a half open top tank for another two years, so most of their lives in open top tanks.....No jumpers if they've got enough space....