too much flow is better than not enough IMO. You can always tune back but its harder to add more. More $$$$$$

I atleast like to run the first part flex, up to the valve and union.

It best to place a union, then the ball valve on the inlet lines in that order, and vice versa on outputs.

If your pump is oversized (wich is best) then i actually like to run rigid PVC after the unions and valves, that way i can tuck it all up tight or beside stuff rather than in my way.
It also makes for a cleaner job.

On OM`s it depends soley on the version drum you have, that would decide for me what type of pipe to use.
If its version 3 Drum , you will want to use spax flex as much as possible on the outlets...This drum version does not like any back pressure, and on a big pump like the 'cuda its hard not to do.
Version 2 i would use either spa or rigid, whatever you would think is better for your scenario...it better drum for the big pumps.

I run 2 OM 4ways, each getting 6000 gph, version 2 is the only option for me, or i would have to opt for more ports open at a time.

Marc.

I ran a dart on my 120. Wicked flow. Closed loop is the way to go unless you have a monster sump. And, you actually can have too much flow, but most people tend to not have that problem. However, if you go with the dart and run it closed loop (which I would suggest), then you will need another pump to feed up from your sump. And if you run the Dart CL, then I doubt you will have significant head loss, in which case you might end up wanting to cut back the flow as some others have suggested. Word of CAUTION :eek: though, if you end up cutting your pump back a third, you run the risk of burning your pump out. Not the kind of money I would "waste" on a nice pump. :sad: I know you want high flow for your sps, but your clams will absolutely hate you for it. You'll be looking to make calm pockets you can stick them in, but if you have tons of flow blasting through your tank, it might be rather difficult. HTH

My understanding is compared to a reef, there's no way we could have too much flow in our tanks, just to much velocity. Could you add more bulkheads for the CL outlets or Tee the ones already in the tank to disperse the flow?

more outlets into the tank would help. Ever considered a surge. That's primo ocean flow. :razz: