My 50 gallon reef system has been up and running for 4 months now and my corals are looking a little stressed. After checking everything I realized that my water flow (current) has really deminished since first turning on the pump. I'm using a EHEIM 1060 running from an overflow, out of my sump and through two powerheads. What is slowing down the water flow? Do I need to service the pump? Is so, what do I do? Any help would be greatly appreciated!