Somewhere on the Krib I read that Amano uses M. angustifolia, reportedly the smallest, shortest Marsilea species. They are all grown pretty much the same, almost like a glosso carpet, and are pretty forgiving in terms of light. They do best with a nutrient rich substrate. This is a marginal plant found mostly in Australia and NZ, and will grow easily emersed.
I have Cladophora in my 55 and I love it - they look like topiary to me. They are good in low-light situations and are very slow growing. You need to rotate them periodically to keep them from getting a brown spot. Eventually they get hollow inside and you can split them and tie them back into ball shapes. No fish pick at it, or try to eat it, and shrimp love to pick through it. They do collect debris so I take them out and rinse them from time to time. They then float for a while and sink again gradually. Lots of places carry them, like azgardens.com, aquariumplants.com, and aquabotanic.com.
