Micranthemum glomeratum. Portion size is at least golf ball-sized, probably more. I have this growing in medium lighting and no CO2. This is a plant with very thin, delicate stems, but it will grow quite fast once it gets settled in. You can plant it in substrate (what I do) or leave it free floating just fine as well. Comes from tanks with snails so I make no guarantees that this is pest-free.