Yes you can. I can appreciate the dilemna as I have tried
repeatedly to grow this "easy"??? plant in my greenhouse.
You would think that high humidity and tropical temps are the things that really make it grow good. But wrong.
It likes the humidity but it dislikes the heat and the light. I finally hit pay dirt when I set a newly purchased plant on the concrete floor! It was really overgrowing its pot and so I set up a pot with some coif (coconut fiber) and buried some of the overhanging branches into it. Wrong!
The branches buried into the coif died!. The plant does not like coif! Don't know if the coif is salty or ??? I use coif for growing tropical moss and the moss has no problem with it.
What I am starting to think is that this Selaginella should be treated like an epiphyte. A loose soil mix maybe lots of humus and large pieces of bark, 60-70% humidity, and 80% (?)
shade. Will have to measure the footcandles on the floor to see how much.
there are other Selaginellas that will respond to the higher temps. I grow most of the tropical ones in closed containers on my greenhouse bench but not S. kraussiana!

So if you are up to experiment you may want to try some that is already potted and plug it pot and all into the darkest corner of your terrarium and see what happens. I would not even water or spray it. Just watch to see what happens. If it fails then it will be the temperature which means that you could try again and add the element of misting it daily to see if the cooler water will offset the high temps.
Apart from that here are the names of some tropical Selaginellas that do well for me in containers.
S. uncinata
S. plana
S. moellendorfii
S. wildenowii

I bought most of these over the net:
Black Jungle and Niche Gardens (these are grown outside there but do so much better inside!).

Hi
Anyone have a clue as to how to tell the various types apart?? I bought a S. martinsii which was a dark green . I have it growing in several locations and in each case the plant is a different color and leaf pattern.
it is now even growing submerged and again the leaf has changed color and shape, It ranges from pink to dark green to almost blue. If i hadn't planted it myself I'd swear it was a different specie.lol
How are the specie separated??
gary

I think that the species are separated based upon the
reproductive structures, basic habit of growth (prostrate or erect), presence of rhizophores (those little root-like things growing out of the bottom side of the stems),the spores morphology, the orientation of the leaves (2-ranked, whorled, etc), general leaf shape (lanceolate, linear, etc.) and natural range of occurrence (such as Africa-but I wish they would say in what kind of habitat such as cool montane fog forests, or lithocarpic in savannas, etc.).
With such a variation in color for the same species why don't you image all the different colored plants and post up a profile of them. I think most of the color variations may be due to the amount of light present and secondarily to the nature of the substrate so indicate how much light and what kind of mix the plants are on!!

click here to see images of Selaginella

I have a red selaginella (it belongs to a friend of mine, she asked me to work my greenthumb magic on it because it keeps wilting and losing leaves) as I suspected, as soon as I had a look at it, it was repotted using ordinary potting mix, now I only have a few types of selaginella so am certainly no expert, and I'm sure there are fully terrestrial species, all the ones I have I grow In the same epiphyte mix I grow my bromeliads in, a mix of medium to fine orchid bark potting mix, coir, and perlite, it drains very well, the coir stores water well but on it's own it tends to rot down very quickly so mixing through the perlite and bark helps create little air pockets and in my experience those little air pockets seem to be where the roots grow most prolifically, I'm situated on the Central Queensland coast and we get VERY hot summers (between 35 and 40 degrees Celsius) the heat never seems to effect mine which are all growing in a very bright greenhouse, I do tend to place them where theyre shaded from the midday summer sun as I've had them bleach a little, especially the tassel fern (huperzia). if I was you I would try a epiphyte mix first, it could be the heat but as I've said mine grow in high temps and well, they're thriving. like most epiphytes they require air around their roots so if u have it in a heavy mix it's most likely suffocating. Hope this helps and good luck, a pic of Ur terrarium would be great btw :) love to see what others are doing.

Gardenerkev, how about posting a photo of the red selaginella. it is hard to know what it is. there are alot of tropical Stachygynandrumous species of Selaginella and so that would explain its tolerance for heat. But alot of tropical ones do not occur in really hot places but in the cooler areas of the tropics, such as S. kraussiana. My best growth of this particular species is outside where it can drop down into the low 40s at night during winter. I have to keep it inside a container of some kind to maintain the humidity. I originally had it growing in my bathroom where it was under 24/7 light. It got too tall for the container so it went outside.