Flow question

[ff.rice]

I'm thinking of going with a 30gallon display tank and a 30gallon sump. What would you all suggest for a return pump size? I know it's normally 4 times per hour.... But does that count for the DT and sump? Or just the DT?

 

[BigRedsReefs10]

You want to match your return pump to your overflow. A little to powerful is better than to weak because you can always dial back the return with a gate valve. And for flow in the dt you want 20-50x tank volume depending

 

[coralbandit]

1 circulation from the return pump should be minimum size accounting for head pressure/loss.The other flow is in current from powerheads or gyres.
Gate valve after return pump big yes!
What type of overflow are you using. This will determine how much flow you can have.

 

[ff.rice]

This is what I'm looking at....1200 GPH internal overflow box https://www.amazon.com/dp/B00OWK75ZM/ref=cm_sw_r_cp_api_Rr5Oyb1NCDP9C

 

[Sniperhank]

That'll be a ton of water movement.
You want a return pump that has more GPH than the overflow. That way a valve can be plumbed in after the pump so that you can ensure that the flow from the pump matches the overflow perfectly. This also helps to lengthen the life of the pump.