Pump size for 300 gallon closed loop system

[HLand]

Any recommendations on GPH for a closed loop system? It has one 1.5" drain and four 1.5" return lines on the back wall of the tank. The display volume is 300 gallons. It has a sump with two overflows and four 1" return lines. Approximate head height is about 4.5 feet. I have the hammerhead/barracuda Reeflo pump but didn't know if that would be an appropriate size. There's at least six 90 degree turns and two T fittings it has to go through. The lower flow setting is max 4500 gph and the higher flow setting is 600 gph.

 

[Vivid Creative Aquatics]

Given the display tank size, and the plumbing, I think that pump will be more than enough to drive 4, 1.5in inlets on a closed loop.

My only concern would be possible starving the pump a bit with a only a 1.5in drain and four 1.5in returns on the loop

The good thing, being a AC pump, you can easily dial back the flow (and thus the need for supply) a bit if you needed to with a simple ball valve.

Are you considering the Random Flow Generator for this tank? They are ideal for closed loop systems and given the amount of supply flow you will be able to produce you could easily flow this tank, with few - to no powerheads.