Hi, I have an Eheim PRO3 2180 and have just done my usual fortnightly change of filter pads but have hit a major problem because after priming the system the pump has not re-started. I've gone through the process five times tonight without success! I have tried to remove the impeller from the chamber but have not been able to remove it as it seems to be stuck.If anyone has experience with these filters could you advise me if the impeller is likely to be the problem in this situation or if not what could be causing the problem? It was operating fine up until tonight,I am able to use the heater but am worried how long my fish will survive without the filter working. The tank is large and is fully stocked with mature rainbow fish. Feeling panicky now, can anyone offer advice please!