PEM, I love South American setups! I think, however, that you should reconsider the angelfish/neon tetra combination. I had a 20 gal planted tank with 12 neons and 6 corydoras sterbai. Everything was honky-dory until I added three quarter sized angels and all my neons became snacks for them. I've had those neons for a while and so was not happy about losing them
. And those angels grew from quarter sized to 4 inches top to bottom within the space of a month
! Those angels were beautiful, but it was bye bye angels for me!