I know they self-prime, but one of my fluval fx5's just shut down. I've unplugged it and plugged it back in and I even waited 20 minutes to see if it would start up again. how long does it take to re-prime itself? I thought it only took a few minutes. anybody else had this happen? I cleaned the filter out yesterday. my other fx5 is working great. no clue what I did wrong.