Tsmit,
bll,
You could have no pipe on the main drain. More height the better IMHO. I think you want to initially set you water level high. Evaporation, blockage, etc. will flow less water (I can't think of any case that would increase water flow) so over time the level may go down. Sock is your choice.
TheFishMan65
I see. My problem would be sump capacity with no pipe. I have a mega-flo design overflo and it holds more water than my present sump would hold (about 10 gallons. It fills up when I shut down the system for water changes). I am starting up my system again after four years away from the hobby so I guess I will set up a larger sump. Maybe a 29H would work OK. What size sump do you use on your 75 gal?