Fluval 300

Is the impeller spinning? If it is not then it may be that the impeller is resting in a dead spot. I've noticed that some older AC filters I've owned do this almost every time I try to start them! I've heard that replacing the impeller may fix this but I simply remove the intake tube and with the filter plugged in tap the impeller with a pen or something. jogging the impeller a bit will get it running again. If this is the problem you are having, be sure to check your filter after power outages as it may not start up then either.
 
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