like Brian, i too, am a fan of perperomias. in fact i have peperomia glauca and peperomia rotundifolia growing in my mantella tank. the other thing about perperomias, is some of them are nice, little epiphytes. i actually have a vine of p. rotundifolia attached to a log and growing out of the water. no soil whatsoever. it is my fastest growing vine in the tank.