I believe Perlite is porous so it should retain some water in addition to it being mainly good for drainage. Is vermiculite similar i wonder. Excellent video gathering together all that information and explaining some i wasnt familiar with. Mixes seem a good way to get properties we need overall. Ive never used Akadama neat as to me it seems to crumble after a year or so in our damp weather. But fares better in mixes. Just my observation.