: Add the gravel first, followed by a thin layer of activated charcoal (if available) to filter the air, then the soil.
: Decomposers (microbes or small insects) break down dead plant matter, returning essential nutrients to the soil. 2. Essential Materials bottle biosphere guide full
Month six, a miracle. The chickweed re-grew, but thicker. Purple. The isopod had multiplied. The blind worm had become visible, threading through the glass like a pale vein. The air inside no longer smelled of rot. It smelled of rain and stone. The Ultimate Guide to Creating a Bottle Biosphere
(Note: If building an , you would use Elodea/Anacharis plants, snails, and shrimp, filled with conditioned water and a bit of sand). Purple
Add 1–2 inches of pebbles or lava rock to the bottom. This is a reservoir for excess water, preventing root rot. Sprinkle a 0.5-inch layer of over the pebbles. The charcoal absorbs phenols and tannins that would otherwise poison the water.