Sumps, external pumps + drilling
 

will an external pump pull the air out of an over the top setup without manualy priming?

want to switch to a used sump i got at the fragfest, my current sump is drilled, and i can drill the new sump no problems i just wanted to save on downtime in between and just fully redo my plumbing in place then just swap the pump over to the new sump when i pull it off. hah still just a "temporary" sump on a "temporary" setup.
temporary as in i want a bigger tank but do not know when it will happen.

Yes, with over the top you have more airflow.
Thats way oldschool though(gratz), remeber its the surface area that lets the co2 out.
Just ensure its agitated and ripply with power heads.

Depends on the pump really but all pumps will at least need an initial prime so it has some water to start, it will not start completely dry. Then depending on the pressure difference, the size of piping and the pump it may or may not be able to prime itself after a shut down. I would suggest a check valve which will keep the pump primed, it will only need to be re-primed if you remove the pump for maintenance.

Meh so far sounds worth drilling. Perhaps it is time to get a backup pump anyways