A classic ingredient in airy soil mixes, perlite is a lightweight volcanic rock that’s been puffed up like popcorn to boost drainage and oxygen flow. It's especially handy for improving water retention while keeping soil light and fluffy - just how we want it for our tropical plants, propagations, and anything that needs a breathability. Just bear in mind it floats and can get dusty, so a gentle rinse before use helps keep things tidy and manageable.