[Delphinus]

Yes. An airlift or an Archimedes screw type pump would have the least shearing effect.

That said ... copepods aren't realy going to be chopped into little bits by pumps and powerheads. Our perspectives on this are skewed a little. If I take my finger and jam it into the impeller of a running pump I can expect it to hurt because, comparatively, my finger is this big immobile object that is going to be hit repeatedly by the blades of the turning impeller.

A copepod on the other hand is tiny. The body will get sucked in and immediately shot out by the centrifugal forces and probably doesn't even ride through the impeller blades for a a complete turn of the impeller. Likely there will be the occasional unlucky one but most of the times they just get shot out a litte dazed and or dizzy but not really dead.