If you want small epiphytic orchids try to look at species like Pleurothallis, Lepanthes and Restrepia. Terrestrial forms are Macodes, Gooyera, Dossinia and Ludisia. They all stall fairly small and like medium temps and good humidity.
Two others I would add are Harella odorata (or retrocalla--both the same) and Psygmorchis pusilla. I'm also having good luck with some of the tropical Dendrobiums blooming and thriving, and I have been having good growth under high light with Slc. and Blc. miniature hybrids. However, we'll see if they bloom well or not.
WEll now there is nothing in the tank, i have four orchids in it, 2 mini oni, and two extreamly small ones the poeple at the orchid shop gave me, she didnt speak good english so i couldnt here the sp, and it wasnt writen down because it was out of her collection.