I'm having a hard time understanding the substrate layering for a planted dart paludarium. Thinking of doing an eggcrate / great stuff build with a waterfall. i am using mesh cups embedded in the great stuff for rooted plants, and planning lots of epiphytes in the upper layers. But for the floor of the land layer, what goes there? I use a mesh soil blocker, then what? coco fiber, leaf litter? How do you layer it? Seems like people do it a lot of different ways...

Also, for the water portion, darts don't swim, correct? So an aquarium gravel might be ok there because they really couldn't eat it, could they?