Hello - Decided to clean out the Sedra 3500 pump to my ER Skimmer during a water change. This time...when turning off the power..there was big intake of water. When I removed the cap, the impeller was frozen/jammed in the pump. I tried pliers and still cannot remove the impeller nor is the pump functioning with power. Has this happened to anyone else and any tips on how to remove? I don't want to exert enough force to crack the pump casing....but the impeller is really jammed in there. Is the pump a goner? Thank you. Doug