Need some advice on a pump for my sump

[HH reefer]

i would go with a mag 9.5, i have a mag 12 on my 90 and i have to keep ball valve half closed or it will suck sump dry

 

[TanksNStuff]

Setup looks odd to me from the pics as well. The one with a bulkhead down low could have been for a return line of a closed loop or it may have been used as a refugium that emptied into a sump right below it?

For what it's worth, I'm using a Mag 9.5 for a return on my 75G tank and I also have a ball valve on the discharge that's slightly closed (almost fully open) and it's perfect flow rate. I have a 1" drain pipe.