I use mag drives in my pond. Great pumps, as long as you like replacing the impeller and impeller housing (due to rubbing) every year (use a good prefilter--made my own). If you get mag drive, don't go smaller than 1800. Problem (here) is not fish poop, but pine needles. They work their way into everything.
I use a via aqua on my indoor sump. Has been running 24-7 for 4 years with absolutely no problems--no noticeable signs of decreased performance. Have not had to replace any parts. No abnormal noises. Not loud inside the stand.
Is the 6-8 feet vertical or horizontal? If it is vertical you are going to lose a few hundred gph. If it is just 2-3' vertical, you might get near 1000 gph. If it is horizonatal with no bends, you will not lose much. But you may look at building 2 sumps with smaller pumps (built in backup if one fails or clogs). What kind of shrimp are these? 2000 of anything is going to need more than 25 gallons.