I've got 12 red head 8 heckelii and 6 blue acara in with 25 black neon tetra and 20 bleeding heart tetra. At this point all had been well but the bigger fish are only in the 3" range id say
Taller bodied tetras should be fine. Just to be on the safe side don't go with narrow or torpedo shaped fish like pencil fish. I keep mine with black skirt tetras and no issues whatsoever.
i'm not sure what species they are, i know they are from Guyana. I will post some pictures of them. but i was thinking 6 geos and 100 Golden Tetras in my tank. Just wanted to make sure the geos wouldnt eat the tetras. These are the tetras http://www.seriouslyfish.com/species/hemigrammus-rodwayi/