I returned from being away for seven days. I noticed that one of my aqua clear filters was not running. Then I realized there had been a power outage; the clocks were off. My generator should have kicked in. It turns out I was out of propane. Stupid me! My neighbor told me the power outage was no more than 20 seconds. How frustrating that the aqua clear filter motor did not restart. Luckily I suffered no losses of fish. It’s strange that my three other aqua clear filters on other tanks were able to restart.