I want to hear your opinion about additional supplemental/viewing lighting for this one. It is kinda hard to decide as this one is unlike regular tank. Pendant style fixture is attractive but must not be hanged too low (or else they will spoil the scenery), I think at least 8 feet high from water level will look great. I saw amano did this with no problem on his giant tank, although his is much closer, more like 4-5 feet away from the water surface.
If you happen to ever been in Singapore's Changi airport, you might remember this indoor fern garden with a koi pond by the terminal. The lighting is supplied by many metal halide downlight very far away (something like 18+ feet away). Yet it is enough to sustain the life of all tree ferns and other kind of ferns (yes, they are real and alive!! and they've been there for more than a year without dying) far below.
Looking at my project condition, metal halide is the only obvious option. With natural sun lighting condition and the nature of plants (non high light plants) to be considered, I'd say 400W bulb would be sufficient to punch through the distance and depth. Two of such bulb would be more than enough to cover the pond evenly.