I would go for a massive amazon biotope. Tons of driftwood, roots, etc. For 10 thousand gallons.... A couple hundred cardinal tetras, fifty or so black neons, 100 silvertip tetras, 150 pencilfish, a huge school of hathetfish. A few pims, some angelfish, and 10-20 of most of the kinds of corys u see, multiple pairs of clown plecos, bristlenose plecos, and a common pleco. Then, a few harems of various apistogrammas. Ive never researched discus, but if they are from south america id get some of those. And a large school of hatchetfish. Then I would plant it with crypts, swords, vals.... Just enough plants to make it seem natural. I dont know if this would be under or overstocking for that large of a tank. My dream is to someday get a 500 gallon tank and do something similar to what i just mentioned.