Have you tried growing the oncidium by a window? I pull my blinds up just enough so that the orchids there get light (and my dogs can bark at chipmunks) but no one can really see in. I also have sheers so that the light can come in but the privacy is there.
I have also tried to grow onc. with my phals but I couldn't keep my phals with my other orchids...they just have different requirements.
Good luck with your terrarium! My son has two snakes and I would love to plop some plants in his aquariums.
Just got my 6500K 26w CFLs today. Just one of these things puts out quite a lot of light. Taking readings with whitegoods iphone light meter I'm getting 13k fc at the Oncidium and 5k fc down at the Phal. I'm sure it's quite a bit less going through the plexiglass and with natural diffusion, but I'm happy with how things look. Now I'll wait and watch the roots grow.