Tank #1: Seems a shame to waste your "beast" of a tank on tiny fish.
Tank #3: You said paludarium is out.
Tank #2: Archers do best with a specialized setup of open air up top for crickets, but it's not a necessity.
With this tank, you could support some larger schooling (shoaling) fish. I used to have scats; the silver ones are beautiful and don't get too huge. My old green scat was great, ate out of my hand. My red scat looked great young, but they are boring brown as adults. They will get really big though, so don't get 6 babies now - they'll overrun your tank, and that 300 gallon is going to seem to be a big hassle.
Now i have 5 mono argentus which school non-stop in the middle level of the tank, and are very hardy. (I know a pro who uses them as a new-tank cycling fish for his cutomers' marine tanks.) A school of 3-4 colombian (bolivian, black-fin silver) sharks on the bottom level is great. I also have 1 jade (sleeper) goby. Another nice schooling fish is the green chromide. they're usually sold 1", but get big. A pair of orange chromides is another option.
With these guys, smaller gobies will most likely become food.
good luck!