Hi
Since charcoal has such a limited effective span in a terrarium About all it does is lighten the soil.. I prefer the so called "false bottom" approach. Lifting the media off the bottom allowing very effective drainage . Many ways to do it
. . Of course terrariums range from" desert. to temperate to lowland tropical. Obviously what you grow would dictate the media.. You can "google terrariums for methods as well as media choices Are you going to keep animals?? . Those needs would have priority over plants of course.
Many many choices lol gary

I definitely would steer clear of the kitty litter, TN -- especially as most litters are formulated to be "clumping" for easier clean up. The last thing one needs in a terr is material that clumps up. As Gary mentioned, the usefulness of activated charcoal is limited though it can be a useful amendment for keeping the soil 'airy' and may provide an additional (though not terribly important) carbon supply for plants.

Even the false bottom is hardly necessary. The only time I would say it is truly a very good idea, is when one is going to be having some sort of water feature that will flow through the soil.

Thanks for your knowledge!

The kitty litter was plain-old fashion kind. My dearly departed Stella, Odin bless her soul (Scandinavian here...), HATED clumping litter and would use the floor - so hence the "vintage litter"

Personally I would not use kitty litter in a terrarium. It's clay,..and when you add water to clay it becomes.....mud! LOL

I never bothered with charcoal and there hasn't been any problem that I've noticed as a result of that choice so I'd just say go without it.

kitty litter is often a low fired clay. If you put some in a glass and cover with water for 24hrs and it hasn't turned to mud, it is fine to use. Actually, it's a fantastic medium. It holds a lot of water while maintaing air space. I use Turface, which is similar, in my terrariums to great effect.

Well that's different! Fired clay pellets WOULD be kinda cool. Now that you mention it crushed pea gravel comes to mind as well. Wish I had some of that...somehow it never gets remembered when I'm out and about.

So for a ten gallon terrarium maybe two inches of crushed pea and sayyyyyyyyyyy 1/2 an in of water at the bottom,but charcoal?...nah. :)