I read that on GARF a long time ago. They once set up a large clean bottom tank with nothing but racks of xenia frags in it and good lighting as a filter for a couple of their 180 reef tanks. They seemed to think it worked real good, and they grew tons of xenia for sale.
Yup, it takes time for a reef system to regroup after a crash type event. but its interesting to watch and experiment with. I seem to be experimenting most of the time.