R&R haha yea pretty much!!!! ;) *R&D!!!! I meant!!!! I think I am not on subject and I am sorry. This is a container froum and the OP wants to use this in a mix for soil less I think the grow stones would be best by them self as a 100% medium as they can probably be reused. So to mix with other things I agree with all the range in size is not the best. "Maybe you should call the company and tell then to not make that product anymore as you know way more then them" ;) I just think many need to have a little more of an open mind thats all. If they decided to make the prodcut they would test it to see if it would work and market, just somthing to think about.

There's a reason you haven't been able to find much if anything on cacti terrs, Jeff -- they generally end in disaster. It tends to be extremely difficult to provide them with the high light they need but not "cook" them in the process & to provide them with the arid conditions they desire. As Gary mentioned, they easily succumb to bacterial or fungal diseases if the humidity is not low. Terr by nature tend to keep humidity in. Hopefully the air circulation you mentioned you will provide will do the trick in that area. Overwatering, ever a danger with most terrs, is an even greater issue with a desert terr. I think Gary's idea of a false bottom is probably something to consider. In that case, you won't want any of you media to actually reach into the false bottom and wick up any moisture that drains there. I look foreward to seeing your set up! Wishing you the best :)

No, i just want a few sections of the terrarium to be able to have mushrooms pop up, or continually pop up, depending on the temp or humidity, I plan on this being the source of oxygen for the plants. Im not sure how much they produce, but im sure it will help more than not having them, i plan on getting a strain that is very small, and can form dense clusters, therefore giving more conversion power from co2 to oxygen. I think i may try out a solid bark mix for about a week or some with a single plant of what i plan on putting in there while i let the rest of what im putting in grow, or germinate. MY MAIN CONCERN is still what kind of substrate to use for a mushroom and plant terrarium.

I do not use any soil in the mix, but even grit could fall/wash out thru drainage hole. I use pieces of mosquito screen over the drainage. Some ppl use plastic canvass (sold in small sheets or pieces in craft stores) - I prefer window screen since the mesh is finer. I cut them to fit bottom of the pot. Some ppl suggests it clogs up - not in my experience (but as I said, I do not use soil). Actually, I use them even when starting seeds in seedling mix (which is fine) if I use bigger pots - do not have any problems, but seedlings are potted up after relatively short time. So maybe not very good comparison... (I can't help with Lithops, but do not believe about gritty soil damaging roots...they grow in pretty harsh 'soils' in wild...it is likely growing conditions? I have seen Lithops handled pretty hard by professional growers - and they lived! I have few in gritty.) ETA: good reading from an expert -Steven Hammer - if you didn't already checked it out :)