Did you take light readings?
I can tell you this, with full sun, things are going to be a problem.
If you have about 90% shading, so roughly 200 umols at noon, then you have far fewer plant issues and algae. Open displays are great, but.........if you cannot control and reduce open green house sun, such tanks rarely last and look good over time.
the other option is add floating plants, they can shade the pond fairly well, but..they block too much light for submersed plants. So a little can work, but not a lot, this is a hard balance to strike with submersed plants under them.
A nicely designed shade cloth mesh over the display would be a wise idea and I would speak to the director/management about it. If they can add more ferns and trees so the pond is shaded more, that would be a good idea also in lieu of the shade cloth. Fixing a large tank with algae issues, well........you'll see.
Set up is one thing, but long term care is quite another matter.
Mostly being able to adjust and modify the light. Light management is 90% of it with larger displays. Most of the plants used can do very well with low light and that will make care over time much easier, thereby a nice display over time.