South American fish please

I would like to get a stirctly South American tank set up.
The tank is a 33 gal planted. Currently housing a pair of angels and a pair of discus. (The discus may be too big in the future, but I have a friend with a larger tank who will take them if that happens, but hoefully I'll have a bigger tank by that time) The angels I beleive are full grown a little larger than the palm of my hand fins and all. The discus are quite small, only about an inch fins and all. There are 2 algae eaters that I would like to move out soon. (they are asian) And thats it.

I would like:
bottom feeders (algae eaters would be nice)
schooling fish (The kind of schooling that when one moves they all move)

I don't want any live bearers in this tank so no mollies or guppies, and I don't want anything bigger than the angels and discus. As that would be too crowded.

And they can't be to rough on the plants, which are needed for cover to hide from the discus fish anyways.

I know thats pretty picky, but any help would be great.

Thanks for the ideas everyone. I'll check out google

Oh, and I had a question. South american fish I'm told prefer acidic pH and softer water. The water from the city taps is hard and alkaline. If the fish are domestically bred and raised will they be alright in this water. That is what they are kept in at the store and I can't aford to play with pH down stuff and chemicals to correct my water hardness. Would it be ok to just keep the water conditions as they are? My angel has never had any problems.