Originally Posted by Gatekeeper
Hmmm. So you force back pressure against the power head to restrict flow? I am not a fan of that, but whatever suits your needs.
In the future, something to consider would be to do what people with sumps do, add in a bypass loop that goes back to the filter. Then by adding in a throttling valve, you force flow back into the filter as opposed to just creating "extra work" and back pressure against something that is not designed for throttling.
Gatekeeper, you misunderstand the physics of how simple centrifugal pumps work.
Doing what you're suggesting is actually more work on the pump than restricting the outflow. Seriously, put it on a watt-meter and check it out.
Common aquarium pumps actually run cooler, and at significantly lower wattage when throttled back a bit (on the output, always)