I would not use any other companion plants. Just stick to the terrestrial orchids that fit your needs. A nice carpet of these kinds of orchids is good enough.
Also tropical forest floors vary around the world. For example in South America the dark and mysterious tropical floor is basically lacking in flora as most of the plants in this type of forest are found as epiphytes or occur on rocky uprisings. Darkness is not a good for a plant to find light and it is that light which allows the plants to exist. That is why the Jewel Orchids can be found in heavily shaded but not not dark portions of forest floors where available light makes absorption of as much of the light spectrum as is possible resulting in the colorful leaves our eyes can see. However, these plants are overwhelmed by high light and can die from exhaustion when exposed to prolonged periods of bright light.

Here is a link that might be useful: One abstract summary of 3 light levels on Anoectochilus

terrestrial man - thanks for that link, that was very helpful as I'm still trying to calculate how much light I am going to need. I was thinking about 500 foot candles would be ok, and it looks like that is on the low end for Anoectochilus formosanus.
I really would like to find an appropriate terrestrial or lithophytic fern and a fern ally though to contrast with the orchids, preferably something that originates in Asia.

Hi
A family I would highly recommend for this type situation is Microsorum. Almost ideal is M. thailandicum.
blue ,jade fern It not only tolerates low light it thrives.lol. In the proper conditions it becomes almost irridescent.taking on an almost turquoise color.Strap type leaves look like they have been polished . In higher light
it becomes medium green higher still higher yellow green.
Many of this family are Asian aquatics but in a humid atmosphere become terrestrial.
Another plus for terrarium culture is that they remain under a foot in diameter. at least for me. I grow them in straight long fibered sphagnum . in a shadehouse though.
All the Lycopodiums that I'm aware of are epiphytic.
How large a terrarium are you doing?? I grow five types of Jewel orchids though slow growing can become quite a patch. lol
I'm converting my 150 gallon aquarium located in the shadehouse into a terraium due to a persistant leak lol
Thes e will go into it for sure.
gary

Gary,
It's funny that you suggested Microsorum thailandicum. I remembered that I had one in another temporary set-up, riding out the winter away from the forced-air heat, and I decided to use it in the jewel orchid terrarium. It really does seem to be a perfect fit with the other plants in there.
I am also going to try Selaginella braunii, even though I don't think it is entirely tropical, it should be close enough, and I love the look of it.
The terrarium that I'm setting up is in an old 75 gallon aquarium.

Hi

Do you happen to know if Microsorum thailandicum and M. steerei are tha same .?? If not what is the difference??
A 75 should give you a lot more room for landscaping. Are you going to add waterfalls mists and all that good stuff??
My 150 that I'm considering is located outdoors so I'm trying to figure out how to control temps ,rainfall.
Wish I could fix it as it made the best planted aquarium I've even had!! Good luck with your setup!! gary

I think Microsorum steerei is a synonym for M. thailandicum, with M. thailandicum being the correct name.
I wasn't planning on having any water features in the set-up. I really just wanted it to look like a small slice of forest floor, with humus, sticks, and a rotting log. Ideally, to be realistic there probably wouldn't be more than a couple of plants in there, but I don't have any self control and it will probably be stuffed full of vegetation eventually - so much for realism.
I'm very limited with what I can do outdoors. I need terrariums so that I can keep gardening during the winter months.
I know it is off-topic, but what species of jewel orchid are you growing?

Hi
Well the Terrarium forum is dead and the orchid forum considers "jewels" ugly step chilren lol So you have to sneak them in somewhere??
I grow L. diccolor ,L. nigrescens ,Macodes,Anoectochilus
and Goodyera.All in pots and the only one in a terrarium is the Macodes. They sort of hang on for me they grow and flower for me just not well.
I recently got some tropical selaginellas at a local show including the red form.!! had been looking a long time for it!! Also some epiphytic Dicranum mosses .
The reason I asked about the Microsorum is that a local dealer swears they are two different species . Steerei being much bluer. Seem to be synonyms on the web .Often find the genus confusing as it's often spelled Microsorium
Seem to be referring to the same plants though .
There moved the post back on topic??? gary

Some very good choices for terrarium ferns are

Microgramma vaccinifolia, reptans, pileselloides, heterophylla, nitida (a little large)
Pyrrosia nummularifolium, pileselloides
Lemmaphyllum microphyllum
Davallia repens, parvula, sessifolia, heterophylla
Tectaria zeylonica

All are epiphytes except the Tectaria and I have been able to grow all in a terrarium in light levels less than 500 foot candles.

There are many more but these are very nice small creeping ferns. There are many terrestrial Lycopodiums but I have not tried any myself. A number of Selaginella would work also. The only Microsorum I would recommend for small terrariums is Microsorum linguaforme.

Hi
Thanks for that list. I'm converting the outdoor aquarium into a terrarium as it leaks. if I can figure out all the problems lol.
I've grown several of the Microsorum species in open containers but mainly the aquatic types.
How is your list for heat tolerance?? That's the main problem for me.
have had no luck at all with any of the orchid famuily in terrariums gary

Hi
Thanks for that website. have been bouncing around the websites but but can't find anybody brave enough (stupid?) to keep a terrarium outside lol
It worked much better as an aquarium than I expected but will no longer hold water. terrarium is all i can think of
but besides the usual problems ther are all the problems of being exposed to the weather. I have some ideas but I suspect come summer it will turn into a vegetable steamer.lol
I did find a site called Orchid board which had a large section on setups. Maybe??? thanks again gary