What do you think the max. pump strenght that can be used after the application of a prefilter that wont have small newly hatched newt/frog larvae get sucked up - if they do, maybe they will go into the stream and fall and by the winter be out of there so that when i drain the stream and fall they can over winter in the pond.

That would depend on the surface area of the inlet as well as the pump strength. If the suction is dissipated over a large area, then animals are less likely to be sucked into the pump. The gph of the pump that you need depends on all the various impediments to the flow that are in the system. I'm too tired to go into all that stuff! Anyway, my site has a new section on keeping animals out of pump intakes at http://www.fishpondinfo.com/pcare.htm I believe. When my big pond was started, the pump we got didn't have enough strength to get the water to come out of the filter so we had to get another one!

I made a 'maternity ward' area in my pond thats the furthest away from the pump as possible. Its a shallow area packed with anacharis and a few other floaters.

Im hoping the adults will spawn there and that the babies will hang out there and survive. I have g/fish and so far they've been spawning and happy. When g/fish spawn, as you know, they lay thousands of eggs - and not all get fertilized - most even get eaten by the adults, or could get sucked into the filter box. There's no way to account for every egg (thank god - or we will have 1 million fish in there every year) so chalk it up to evoluion if some get sucked into the filterbox and perish. :(