Interesting . . . . anyhow . . . as for my experience. Everytime I move the pulsing xenia's towards higher lighting with low flow rate they pulse more than where I move them lower in the tank . . . not sure if lighting has anything to do with it but from my experience thats what happens. . . . Most fish store tells me that they pulse depending on the level of your iodine in the tank and the quality of your water. . . Again I have no proof of that so ... not really sure
