Starting seeds in vermiculite or perlite is similar to starting in soil but there are a few differences you need to be aware of. This article is a companion article to starting in soil which you should read before this one.
Choose perlite and vermiculite instead of soil if you want to skip the insect eggs and other contaminants that often come in a bag of soil.
Unlike starter soil, perlite and vermiculite have no nutrients in the medium whatsoever, which means you have to add the nutrients. To do this you should supplement the water you use with nutrients to make it 300 ppm. 300 ppm is the ideal amount of nutrients for seeds and seedlings.
Perlite and vermiculite do not retain water as much as soil does and have the attribute of superior water distribution. Perlite distributes water very evenly throughout the container and it drains very fast. Vermiculite has some water distribution characteristics as well. It retains water longer than perlite does, but not as long as soil.
Vermiculite and perlite can be mixed together to create your own custom ideal level of water retention and drainage.
You can sterilize and reuse vermiculite and perlite. A 35% hydro peroxide / 65 % water solution followed by a clean water rinse is effective for sterilization of used perlite or vermiculite.