[Delphinus]

As a total random interjection here, I truly doubt the veracity of claims that pumps are that damaging on plankton. I'm sure some don't survive the trip, but many do and I bet it's safe to say that most will. Just look at how it happens. Copepod dances a little too close to powerhead input, gets sucked in, gets spit out about 10 ms later, maybe a little dizzy but otherwise totally intact and totally alive. It's not like the pump is a blender where the contents are held in place by gravity and repeatedly beaten into a liquified pulp by the blades.. I bet the copepod just hitches a ride in the gaps between the impeller blades and doesn't even make a full rotation before exiting. I'm sure some are chopped of course, but I honestly doubt that pumps and skimmers really have any large impact on the population numbers of plankton/copepods/etc. in a tank, since they prefer to crawl around substrate anyhow..