Miniature terrariums need actual drainage, not just pretty rocks

I started building tiny terrariums 8 months ago and have killed 4 setups because every tutorial online skips the real drainage layer. Everyone puts a few pebbles on top of the glass and calls it done, but moss and soil still get waterlogged from below in about 3 weeks. I tested a 2 inch gravel base with a mesh separator against a 1 inch pebble layer, same plants, same light, and the difference was obvious by day 19. The mesh costs like $3 at a craft store and stops the soil from sinking into the gravel, which is the whole problem. Why does nobody mention that the charcoal layer is useless unless the water can actually reach it? Has anyone else lost a landscape to soggy roots before they figured this out?

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wright.jesse1mo ago

Did you try adding a layer of filter fabric between the gravel and soil before you got the mesh? I lost my first two setups the exact same way, and I felt like an idiot because the fix was so cheap and simple. The water pooling at the bottom just sits there if the soil fills in all the gaps, so the roots basically drown slowly. I also had to stop using sphagnum moss as the top layer because it held moisture like a sponge against the glass. Your test sounds way more controlled than my trial and error, but I'm glad someone finally said the obvious thing out loud.