Good idea Jim.
Russ my mag 5 that was feeding my chiller was 3 years old. It works fine, I have always kept it clean. When I opened the pump the rust was all over! I can't even begin to tell you the awesome SPS that I lost
The day after I removed the pump it was like a breath of fresh air. With in a week colors and growth tips returned and most importantly no more STN/RTN