echoofformless
Peat Advocate & Defender Of Snails
I run a Whisper on my 5.5g. It works wonderfully. Never owned an Aquaclear personally, but so many people on here swear by them that I figure they must be as good as any.
When in proper condition, no HOB filter should empty to a point to where it can't start back up again after a power failure. I often unplug all of mine while doing maintenance and when I plug them back in; they come right back to life.
With HOBs it will sometimes require some noisy "sucking" time to get back up to speed but it will always be functioning again within a minute or so. Otherwise it's malfunctioning. The only time it might not be able to start back up is if the water level in the tank is really low.
I'd return it and get an Aqua Clear. Skip all others, they freeze up when under 74 degrees. :joke: