I have a Varios 6 as my main return pump. I run it at 100% and only change it during feeding. I have it run through a Neptune Apex flow meter and when first installed it got over 500 gpm of flow. Previous to the 6 I had a varios 4 and it did this exact same thing. As you can see from the graph, the flow continues to deteriorate. I take the pump out, clean it, clean the piping, clean the flow meter and I never get back to even close the original flow I got with it. The deterioration of flow the meter shows is correct as I have to keep closing off my drain valve to keep the water lever up to the emergency drain. Is this normal? I've had two varios pumps do it now. Thoughts?