Originally Posted by hoppycalif
Cannister filters don't have a head pressure, other than the height of the top of the tank to the water level in the tank. In fact, the type of pump they all use doesn't generate more than a few inches of head pressure. When you put lots of filter media in them, that can cause the pressure in the pump to drop below atmospheric pressure, causing cavitation, which damages the pump. They are designed so it is very unlikely that you would have that much filter media.
Thanks, I didn't know that. Learning something new every day, it seems. So, if the pump is rated at 525gph, what would that work out to in real-world gallons per hour? Also, how much turnover should I expect on a tank, 5x per hour? 10x? The last time I had to think about this stuff was back in my reef days, and I'm reeealllly rusty on it.