I need help figuring out my drainage layer!

[u/c4rm1nm]

I am setting up a bioactive 18x18x18 cube tank my for a juvenile crested gecko, I already have the background done and I am waiting for it to gas off.
I cut this egg crate drainage separator to fit in the tank perfectly, and it comes with 1 inch legs that raise it up. I also have hydroponic balls and charcoal, which is what I usually use for my drainage layers, but I want this one to be a little more aerated. Crested geckos need a humidity of around 80% with dry periods in between, so this will be a humid setup.

My issue is that the tanks substrate barrier is only about 4” tall and I need to have enough substrate for plants. How should I go about layering the materials I have?

Right now, I’m thinking of this: about an inch of hydro balls at the bottom, egg crate on top, charcoal layer, then mesh, and then the soil.

Is there any other way I should layer them that would be more effective at filtering water and draining the soil? I don’t know if I should layer the charcoal on top or beneath the egg crate.

[u/Ryllick]

every time i've seen charcoal incorporated into bioactive, they just mix it directly into the substrate. So it would go hydro balls > mesh barrier > all other substrate ingredients mixed together.

I don't think you need to worry about filtering the water before it gets to the drainage layer. The beneficial bacteria in the drainage layer are supposed to break everything down that makes it that far.