Yup, my cacti terrarium looks as good now as when I planted it, which has to be over 18 months ago. I remove the stopper in the top for much of the summer when the cacti are watered, but it stays in over the winter when I keep them dry. I do occasionally see a small amount of algae growth along the sides but it always dies off after a brief break from watering.
I'd love to see pics of yuor bowl and water plant Calin, I'm sure there's far more upkeep with one of those to keep the water fresh etc.
