Well if you had some small bark trees/branches in there, you could mount some miniaturish orchids on them which don't require temperature drops to initiate flowers. I.e warm growing orchids such as aerangis.

A few things to bear in mind are that plants need more light in the 420 to 700nm parts of the spectrum(i.e not uv like lizards) and they'll also need constant air movement.

Otherwise I don't see why it wouldn't be possible. You could have bark substrate around the pool, with orchids growing around that, ferns, bromeliads, carnivorous plants etc.

RP1

Thanks, I guess I was just worried about the tank not being tall enough, I thought they could only be in tall tanks, but thanks for the reassurance. I would like to know what kind of light you would suggest for that kind of set up, I can probably get one cheap through my aquarium friends. Constant movement, how would I go about doing that? Thanks

You'd need a fan for air movement. Light setup for that height could be either cfls or plain fluorescent tubes(t8's or t5's). Long tubes would probably be best though.

Just make sure the orchids you grow in there are miniatures and warm-intermediate growing, i.e aerangis, schoenorchis, haraella, epidendrum porpax, miniature angraecums etc. Those that require winter rests should also probably be avoided(I'm going to try them and see).

RP1

you can do nice things with a 20 gal and carnivorous plants work well in one

{{gwi:1272030}}

this is my terrarium also a 20 gal

Here's my 20 gal terr:

{{gwi:1272031}}

Not exactly critter-friendly, and too many plants jammed into it, but it's really just a holding tank for my terr. plants at the moment, since I downscaled from an 85 gal terr. and haven't gotten a new tank yet.

I'd go with a very small fan for such a small tank, and you wouldn't need serious lighting, either. I've got two fixtures on mine, with a total of two bulbs and 80 W. 15 of that is from a regular fluo, and 65 from a power compact. Aim for a colour temp of 6500-6700K, and my amount of light is enough for med-low light orchids. If you want a good list of them, go to www.andysorchids.com. You'll get a long alphabetized list of minis with their culture requirements, so you can tell which ones are warm growing. And since you've got a 20 gal long, I'm guessing it's shorter than mine, so you may need even less light (since the plants will be closer to the light source).

Could you go Even Smaler lets say a 10 Gallon tank? I think it would kind of cool but a hassle. I exspecialy want to see a moss coverd floor with a few small tree like suculents (tropical of course) it would look very cool, but $$$ is a lil short right now but thats the way things go. And i would love to do a CP Terrium but Most the tropical need more space, and that again requires money. But Any Relitivly ~Cheep~ set ups that can be held in a small 10 gallon tank? (their have been a few sales at Walmart and pet stores near by )

Thanks