Im in the process of adding 'live plants' to my crabitat, you can use many non-toxic plants such as:
Bromeliads ....

Baby Tears ....

and I know of a fellow crabber who has pothos in their crabitat ....

Im hoping to have some pics within the next month of my completed live crabitat, will post them here for your comments as soon as Im finished, hope that helped you a little
Kellie

Just one word of warning though, if you buy your plants be sure to re-pot them to be sure there is no fertiliser or foreign matter within the soil, I re-potted mine in coco-fibre, watered with dechlor water and have kept them away from my pets, and wild birds, I would also recommend letting them 'sit' a while before adding them to the crabitat just to be sure that there are no traces of fertilisers or pesticides
