Hi Jester,
Opinions vary widely, but I'd say a general rule of thumb is having a turnover flowrate 5 to 10 times your tank water volume.
In your case with the new 160.... around 1600 gph. This turnover is normally the amount of water moving through the sump/pump/tank/overflow COMBINED with the internal flow from any powerheads placed within the tank.
Some people go higher, some go lower.
If you go higher flow through the sump system, you may not need as many powerheads in your reef tank.
If you go lower than this, you may find you need to add powerheads for enough internal tankwater circulation.
I'd say anywhere from 8 to 12 turns per hour is more common.
You may want to think about the sump volume in relation to the flowrate returning to your tank too, and how your choice of overflow can affect the way the whole thing performs.
You must allow some room in sump for the water to drain back down when the pump is turned off, or when you lose power. The sump must be able to handle this amount of water, or it will overflow under the stand.
I'm not sure how much you've looked into this, but you should drill a hole in the spraybar just under the normal tankwater level. When the power is off, the tankwater will begin to drain (siphon) back down to the sump. It will continue to drain until the spraybar sucks in some air. It sucks in air as the water just begins to drop down to this drilled hole.
Then you hear and see it break siphon, and no more water drains down to the sump.
This drilled hole(s) is even more important if you have your return spray fitting deep down into the tank.
The other thing to think about is if the sump's too small, and you have a large tank in comparison, and a large return pump ... when you turn on the pump it will begin shooting water up to the tank, and the sump level will drop.
The overflow must start seeing this tankwater rise, and have water start draining back down to the sump, BEFORE the sump level goes down too far and the pump starts sucking air.
I don't have nor have I ever set up 160 gallon tank, overflow, sump and return pump, so I don't have direct experience.
If I had your set up and was going for a reef tank, I'd want a lot of flow as I have on my 75 tank.
It would cost a few bucks to set up, but I'd consider having (2) 1400 gph LifeReef Prefilter/Overflows, and (2) MagDrive 12's, each putting out around 1100 gph at say 4' head.
Run one pump 24/7 giving you close to 7 turns per hour.
Set the other pump on a timer and vary it's run time.
With both pumps running - you'd be around 13-14 turns per hour.
I'd get a larger sump too with this set up as well.
That would be a nice set up in my opinion, that you could play around with.
Of course - this is my view and what I might do in your shoes. Or not, I haven't looked into a 160 before. But I do like a lot of water moving through my tank and equipment ... and am not particularly fond of powerheads in the tank.
My approach is not the norm.
Lastly, many people would not want that much flow, and would choose lower flow return pump(s) and overflow(s) to set their system up the way they wanted.
If you're already aware of this stuff, then I apologize for such a long windy reply.
See ya
