What size pump

Also to clarify are you referring to just sump flow or overall flow in the tank?

I like 5x-10x the display volume through the sump but 30x+ overall in the tank depending on what you plan on keeping in the tank, what type of coral etc.

What are you talking about running off the return pump? Other equipment, like a reactor, or maybe a skimmer, or are you just talking about running all of your in-tank flow from the return pump?

 

i was talking about running off the return pump in my wet/dry to the Other equipment, like a reactor,skimmer,refugium, No im not talking about running all of my in-tank flow from the return pump.

 

I see, well you'll have to do some research and some calculations unless you know exactly what equipment you want it's impossible to size one appropriately, it totally depends how you're going to plumb it all together and how much flow each piece of equipment is going to need. You could just get a big pump and dial it back with valves but that might be more expensive than you want.
It really depends on the exact equipment you want to use. Especially if you want to run a skimmer off of it, there are only certain skimmer designs that will work with being run off a manifold from the return pump and they'll need different flow rates depending on which one you get.