On the smaller AC's like the 200's and 300's, that was a problem but since they renamed them to AC 70, 100, etc, I haven't had a problem with them restarting. With the larger filters, the water inside pretty much stays level and as long as your tube is DEEP into your tank I don't see a problem with the motor burning out.
Your quote made me want to make or buy (if they're available) an extension to put on the filter to make the intake even deeper into the tank, that way I don't have to stop the filter when I do water changes
Yes they do sell extentions for the intake. You should be able to pick one up at your LFS or at least have them order you one. You also may be able to find one online. I have an extention on both of my 500's so that they are about 4" off the bottom of my 90 gallon.
I use ac on all of my tanks... No problems aside from w/c cause the filter will syphon out to the tank when the water level drops so i have to fill it back up with a cup... Highly recomended though...
My experiance with HOB's has been mixed. 70% of the time they restart after a power outage. It depends on how dirty the inside of the filter is. I have had a filter run all day of over night after a power failure without suction. I have never had a motor burn up. I work in the maritime industry and deal with very large pumps. The impeller will get ruined long before the motor will burn up on your small aquarium pump. I always question people who claim their motors have burned up. The water in my HOB's does not even get that a warm after the impeller has been spinning all night without suction. As with most small motors, they are air cooled.
As for running it dry, this is magnetically driven pump. As such, there are no moving parts in electrical section of the motor. I let mine chug as I cup in tank water. Would not do it for a long period though.
