Hi
I use a false bottom in my large terrarium so use no potting materials at all . They are sustained hydroponicly.
I do use the clay pellets for some orchids but I find they are no better than crushed lava stone and cost about 3 times more. Both will last indefinitely
Charcoal will absorb all kind of stuff but this condition
is very short lived. Unless you intend to renew it on a regular basis not worth the expense.IMO.
IMO Hydroton (clay pellets0 are better than airaflor due to a lot less dust.
Since there are dozens of kinds of terrariums with dozens of kinds of plants not to mention animals . There are dozens of methods. Most anything will work for some length of time so the real ?? is which worked best in my situation?? In my situation i prefer the false bottom hydroponic method with very limited media .
Would help a lot to know what kind ans size of terrarium?? gary

I've heard the same thing about clay pellets. Any specific brands you would recommend?

Hydroton is the type I have had the most success in locating around me. Check for local hydroponics stores in your area -- why pay for shipping if you don't have to?

In my terrs I used lava rock (rinsed)as I did not want to incur the expense of using the puffed clay. I do use the hydroton for my orchids however, as I think it does a better job of wicking than lava rock.

Hi
IME Hydroton I've bought bags of airaflor(spelling) that were half dust. Locally it costs around 12 bucks for around a gallon while I can get crushed lava (black as well as red for around 6 bucks for 2 cubic feet.
I use these materials for mostly tropicals but are not grown in terrariums. My only one is a 75 gallon paludarium with 12 incjhes of water. terrestrial plants are epiphhytes grown on emergent driftwood.
I have started a 150 which will be used for terrestrials
but so far only contains Cutting from various tropical plants. I'm going to use a false bottom with a background of X foam it will be heated and will be exposed to rainfall.
i don't grow the types of orchids that would appreciate this type of setup but heck half the fun of a terrarium is experimenting??? gary