For me, it would have to be a center feature in a huge room, tbh i would love to have my on aquatic shop!
I would want the tropical pond to be minimum size of about 8-9 meters long and at least 5-6 meters wide and about 2 meters deeb although i would probably want it sunk slightly into the ground but with a ledge at floor height of about 50cm wide around the inside before it drops down.
It would have to be bottom draining, kind of like a swimming pool system and have the return flow coming back in via a waterfall if possible. I would have extra thick reinforced glass window panels in the sides, maybe a step/ledge to sit on running round edge of pool and if in shop then maybe perspex/glass panels errected round top of pond because as much as some kids deserve to be fed to the fish, it might make the water quality quite poor
Fishwise, an Arowana would be a MUST have! I would also call round shops and offer to rescue 1 x Red Tailed Catfish, 1 x giraffe catfish and maybe 1x perruno catfish, just because these poor gorgeous beasties are just sitting in tanks desperate for more room!
Would also tank on 3-4 Pangasius too! And i would love a Tiger Shovelnose but would settle for just the normal smaller shovelnose.
Would love a larger snakehead species too if possible but it would have to be a case of add them and see how they all interact, i know at our Reading branch they have a tropical pond with an Aro, 3 Pangasius, a couple of Pacus, a RTC and 2 Giraffe Cats and some big plecs and a couple of other oddballs.
All fish would have to be rescues though, to help out all other shops needing to move fish on.