Definitely skip the water feature. You are already pinched for space. Water features are for you...to look pretty. Your frogs want more real estate. That is valuable space better used for more leaf litter or a nice piece of climbing wood. I like ghostwood.
No cleaning involved other than wiping your glass down. As Drew advised, bugs will be your janitors. In addition, your live plants use the frogs waste as fertilizer and clean the soil through growth.
When you are ready for some info on cultivating your viv "janitors", check this thread out. http://www.dendroboard.com/forum/foo...ringtails.html