The videos are pointless, just someone trying to flog their own leaves. Basically, the leaves are often used to lower the PH/recreate blackwater conditions in tanks, and the tannins and humic acid that the leaves give off are supposed to be beneficial to the type of fish that thrive in those conditions. I use them in my 200L tank, and basically, I soak them first for a few weeks to get them waterlogged so as they don't float back up, and to cut down a little bit on the tannin. Even by doing this, they sometimes can be a bit feisty, so I usually sprinkle a small handful of tank sand on top of them when I put them on the bottom to keep them down. All I know is that my apistos and plec love them