I like a decent sized school of neon tetras, every time I've had them they're extremely hardy, and the bichirs eat them almost immediately after being put in the tank. But to be honest whatever hardy fish you can find willl work, if you're buying from a chain store I would seriously recommend a quarentine in a smaller tank until you're sure they don't have anything. Last thing you want is to start off a fresh tank needing to combat something.
Also I forgot to ask in my last post, have you chosen a stock for the tank yet?
Also I forgot to ask in my last post, have you chosen a stock for the tank yet?