Need advice on 2,000G public tank

Hi all-
I work at a major botanical garden that has recently installed a native Florida habitat. A 2,000 gallon "vivarium" was installed with the purpose of hosting turtle species, but the idea had to be abandoned. Now they want it to be planted and have fish, all native to Floridian (fresh) waters.

I have experience with planted aquaria in the home, so I was assigned the task of figuring out how to make this work.

I have many questions, and I'd be happy if any one of them could be answered or if someone could point me in the right direction-

1. Do I need a heater for South Florida freshwater fish? Do they make heaters for tanks that large?

2. Can I plant submerged plant species in five foot deep water? It is in a greenhouse, so there is plenty of natural light- the front of the "tank" is a wide bow front.

3. If I *can* plant stuff that deep, do I need supplemental CO2, or is movement of water via powerhead sufficient?

4. If I *can* meet the above requirements, how often will I need to drain the vivarium in order to be able to remove dead leaves from the plants/perform maintenance?

5. The walls are made of limestone, but I'm assuming that with that volume of water, pH could be easily controlled via chemical addition if monitored properly?

6. Does anyone know of any sources for strictly native Floridian submerged plants? I've contacted The Florida Aquarium in Tampa, and am awaiting their response.

Many thanks for any help that you are able to give.