Water quality should be excellent, as is the case with any other fish you keep.
There are a few tetras that are not from the South American region (ex. Alestiidae family), but most of the common ones you see at pet stores are. Make sure you check on individual species if you're determined to have a biotope- as Menagerie said, there's a lot to choose from!
Filtration is dependent on the size of the tank and the number and kinds of fish put in it. Many people use filters the next rating up from what would be considered "normal" for the tank size.
Decor could be dependent on what individual habitat you select from amid the South American possibilities, or you could mix and match among that group. The Monga Bay site linked to above also has an excellent informational page on biotope aquariums that you can see here:
http://fish.mongabay.com/biotope.htm.
One of my favorites and one of the hardiest fish from South America that you may want to consider is the Bolivian ram (
Microgeophagus altispinosa), a small, peaceful cichlid that acquires quite an astounding array of colors and has very interesting behavior! If this is the 33g Menagerie mentioned, this fish would fit right into the lower and middle levels.