Yup, all my phrags, even my wallisii, sit in 1/2" of rain water or RO; changed out every week. Mini Grande grows in a light stand under two T-12's, flushed with water once a week, usually a "top-up" of water mid-way between waterings. I use 1/2 RO & 1/2 150 -300 ppm tap water in the winter; 1/2 Rain water & 1/2 same tap water in the spring & summer. Fertilize infrequently (when I remember that is) with Dyna-Gro Grow 7-9-5 and Dyna-Gro Bloom 3-12-6.
This one did not bloom in 2011; but like all my other phrags, had been plagued with thrips. I'm hoping we've turned that corner...only saw a single thrip during last watering...