Hi,
sorry for the late answer, but I was in Germany and just now leaving for judging discus in KL (at the AQUA FAIR in Malaysia) and for lectures there.
For your (nice) 650 liter aquarium have also a look at my Nanay decoration at:
Bleher's Biotopes on my website
http://www.aquapress-bleher.com/inde...d=99&Itemid=64
I would have at least 6-8 greens from Nanay in it (up to 10 is also ok, if you can afford it); some 5-6 angelfishes (if possible wilds from Peru), if you want a group of 8-10 Corydoras (best leucomelas or arcuatus); you can also have some nice Apistogramma bitaeniata in it (not biotope correct, but still nice); you should have some larger loricariids like Panaque species (about 2-3), 3-4 Rineloricaria or Loricaria spp., and if you want a couple of smaller freshwater stingrays (Tiger). If you want chacoids, i would take Petitella georgiae - a group of at least 15 (better 20-25), that will make it very well and they are much more group oriented that Boehlkea fredcochui.
Make sure you have fine white sand on the bottom and have some nice driftwood (well watered).
All the best now,
always
Heiko
www.aquapress-bleher.com
www.aqua-aquapress.com