Terrarium out of a 60 gallon tall aquarium help

Out of curiousity I did a search on this horticultural charcoal and happened onto Paghat's website. I was a little surprised to find that horticultural charcoal has absolutely none of the properties I thought it had. I was going to put a layer on the bottom of the tank, covered with a layer of weed fabric, then some pea gravel mixed with sand, covered that with more fabric, then on top of that the promix. I want to grow a number of things, all needing similar conditions, low light, and dwarf. In one area I'm putting in a little zen area with raked sand and some miniatures, etc.
So, is it my understanding I can eliminate the charcoal? Do you have any recommendations regarding what mix ratio, etc? One last, can I assume if only one fluorescent tube full spectrum 4' light would be considered a low light situation if the tube is more than 24 inches above plants. Is this a correct assumption?
Anyone with experience or knowledge is welcomed to give some advice. I somehow think Paghat knows more than most people on the Internet...or it looks to be so.
Victoria
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wrote:

You can use a layer of aquarium filter charcoal. The charcoal is often used in terrariums to help keep the soil fresh. If you are very careful about not over-watering you can eliminate the charcoal. A typical fluorescent tube 12" away is low light. I keep African violets 2-3" from the fluorescent tubes to keep them blooming--any further than that and blooming is greatly reduced. To be sure about the number of lumens use a light meter. I found the most challenging part of a terrarium is keeping the plants small with monthly manicures. Pick plants that stay small and enjoy the kind of environment you are creating. I found that Baby's Breath is difficult to grow, but inside a terrarium it grows exceptionally well.
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From what I read this step of charcoal is useless and unnecessary altogether. I never overwater anything. What do you mean by Baby's Breath? Do you have a botanical name?
I do not plan on using any flowering plants and all will be determined as low light...understory in nature, generally having red undersides to capture as much light as possible.
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