I have two Hydor 2450 powerheads in my mixed reef 180. One at each end of the tank (6'). Mid-tank pointing back. They alternate sides at 15 minute intervals. (I also have the 4 return heads). The corals are predominantly softies. Is this enough flow? Should I have them on at the same time? Should I opt for longer duration? Should I add another head that is on constantly? TIA.